Channel equalizer and method of processing television signal in dtv system

ABSTRACT

A channel equalizer includes a channel estimator, a coefficient calculator, a multiplier, and an error remover. The channel estimator estimates a channel impulse response (CIR) of input data in which a known data sequence is periodically inserted. The coefficient calculator calculates equalization coefficients using estimated CIR, and the multiplier multiplies the input data with the equalization coefficients for channel equalization. The error removes estimates a residual carrier phase error of the channel-equalized input data and removes the estimated phase error from the input data.

This application claims the benefit of the Korean Patent Application No.10-2006-0064982, filed on Jul. 11, 2006, which is hereby incorporated byreference as if fully set forth herein. Also, this application claimsthe benefit of the Korean Patent Application No. 10-2006-0089736, filedon Sep. 15, 2006, which is hereby incorporated by reference as if fullyset forth herein. This application also claims the benefit of U.S.Provisional Application No. 60/884,204, filed on Jan. 9, 2007, which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to digital television (DTV) systems andmethods of processing television signals.

2. Discussion of the Related Art

Presently, the technology for processing digital signals is beingdeveloped at a vast rate, and, as a larger number of the population usesthe Internet, digital electric appliances, computers, and the Internetare being integrated. Therefore, in order to meet with the variousrequirements of the users, a system that can transmit diversesupplemental information in addition to video/audio data through adigital television channel needs to be developed.

Some users may assume that supplemental data broadcasting would beapplied by using a PC card or a portable device having a simple in-doorantenna attached thereto. However, when used indoors, the intensity ofthe signals may decrease due to a blockage caused by the walls ordisturbance caused by approaching or proximate mobile objects.Accordingly, the quality of the received digital signals may bedeteriorated due to a ghost effect and noise caused by reflected waves.However, unlike the general video/audio data, when transmitting thesupplemental data, the data that is to be transmitted should have a lowerror ratio. More specifically, in case of the video/audio data, errorsthat are not perceived or acknowledged through the eyes or ears of theuser can be ignored, since they do not cause any or much trouble.Conversely, in case of the supplemental data (e.g., program executionfile, stock information, etc.), an error even in a single bit may causea serious problem. Therefore, a system highly resistant to ghost effectsand noise is required to be developed.

The supplemental data are generally transmitted by a time-divisionmethod through the same channel as the video/audio data. However, withthe advent of digital broadcasting, digital television receiving systemsthat receive only video/audio data are already supplied to the market.Therefore, the supplemental data that are transmitted through the samechannel as the video/audio data should not influence the conventionalreceiving systems that are provided in the market. In other words, thismay be defined as the compatibility of broadcast system, and thesupplemental data broadcast system should be compatible with thebroadcast system. Herein, the supplemental data may also be referred toas enhanced data. Furthermore, in a poor channel environment, thereceiving performance of the conventional receiving system may bedeteriorated. More specifically, resistance to changes in channels andnoise is more highly required when using portable and/or mobilereceivers.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a Channel equalizerand a method of processing television signal in DTV receiving systemthat substantially obviate one or more problems due to limitations anddisadvantages of the related art.

An object of the present invention is to provide a Channel equalizer anda method of processing television signal in DTV receiving system thatare highly resistant to channel changes and noise.

Another object of the present invention is to provide a Channelequalizer and a method of processing television signal in DTV receivingsystem that can also enhance the receiving performance of a digitalbroadcast receiving system by using pre-defined known data already knownby the receiving system and the transmitting system in a channelequalization process.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, achannel equalizer for use in a digital television (DTV) receiving systemincludes a first transformer, a channel estimator, a second transformer,a coefficient calculator, a multiplier, a third transformer, and anerror remover. The first transformer converts input data in a digitaltelevision (DTV) signal into frequency domain data. The input datainclude main and enhanced data and a known data sequence is periodicallyinserted into the enhanced data. The channel estimator estimates achannel impulse response (CIR) of the input data using a trainingsequence which is identical to the known data sequence. The secondtransformer converts the estimated CIR into frequency domain data, andthe coefficient calculator calculates equalization coefficients usingthe frequency domain CIR. The multiplier then multiplies the frequencydomain input data with the equalization coefficients for channelequalization. The third transformer converts the channel-equalized datainto time domain data, and the error remover removes a residual carrierphase error from the channel-equalized input data in the time domain.

In another aspect of the present invention, a digital television (DTV)receiving system includes a tuner, a demodulator, a known data detector,a channel equalizer, a block decoder, a Reed-Solomon (RS) decoder, adata deformatter, and a data processor. The tuner tunes to a channel toreceive a digital television (DTV) signal including main and enhanceddata. The demodulator demodulates the DTV signal, and the known datadetector detects a known data sequence which is periodically inserted inthe enhanced data. The channel equalizer performs channel equalizationon the demodulated DTV signal by removing a residual carrier phase errorfrom the demodulated DTV signal using the detected known data sequence.The block decoder performs trellis decoding on main and enhanced datapackets included in the channel-equalized DTV signal. The RS decoderperforms RS decoding on the trellis-decoded main and enhanced datapackets for first forward error correction (FEC). The data deformatterdeformats each RS-decoded enhanced data packet, and the data processordecodes the deformatted enhanced data for second forward errorcorrection (FEC).

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a block diagram of a channel equalizing deviceaccording to an embodiment of the present invention;

FIG. 2 illustrates a detailed block diagram of a remaining carrier phaseerror estimator of FIG. 1;

FIG. 3 illustrates a block diagram of a phase error detector of FIG. 2;

FIG. 4 illustrates a phase compensator of FIG. 1;

FIG. 5 illustrates a block diagram of a demodulating unit of a digitalbroadcast receiving system according to an embodiment of the presentinvention;

FIG. 6 illustrates a block diagram of a digital broadcast transmittingsystem according to an embodiment of the present invention;

FIG. 7 and FIG. 8 illustrate another examples of data configuration atbefore and after ends of a data deinterleaver in a transmitting systemaccording to the present invention;

FIG. 9 illustrates a block diagram of a demodulating unit of a digitalbroadcast receiving system according to another embodiment of thepresent invention;

FIG. 10 illustrates a block diagram of a digital broadcast transmittingsystem according to another embodiment of the present invention; and

FIG. 11 illustrates a block diagram of a digital broadcast transmittingsystem according to yet another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. In addition,although the terms used in the present invention are selected fromgenerally known and used terms, some of the terms mentioned in thedescription of the present invention have been selected by the applicantat his or her discretion, the detailed meanings of which are describedin relevant parts of the description herein. Furthermore, it is requiredthat the present invention is understood, not simply by the actual termsused but by the meaning of each term lying within.

In the present invention, the enhanced data may either consist of dataincluding information such as program execution files, stockinformation, weather forecast, and so on, or consist of video/audiodata. Additionally, the known data refer to data already known basedupon a pre-determined agreement between the transmitting system and thereceiving system. Furthermore, the main data consist of data that can bereceived from the conventional receiving system, wherein the main datainclude video/audio data. More specifically, in a digital broadcasttransmitting system for multiplexing main data with enhanced data havinginformation included therein known data having a pattern formed inaccordance with a pre-arrangement between the receiving system and thetransmitting system may also be multiplexed and transmitted.

At this point, the known data sequences having the same pattern may beperiodically inserted and transmitted in enhanced data packets (orgroups). Alternatively, known data sequences having different patternsmay be periodically or non-periodically inserted and transmitted in theenhanced data packets (or groups). Such information may either bepre-known by the receiving system, or be transmitted along with theknown data sequences from the transmitting system. Furthermore,additional encoding, such as block encoding, may be performed on theenhanced data. Also, in order to enhanced the receiving performance, anerror correction code having better performance than the main datasection may be applied to the enhanced data processed with additionalencoding and the known data that are not processed with any additionalencoding.

By using the known data transmitted as described above in processes,such as carrier synchronization recovery, frame synchronizationrecovery, and channel equalization, the digital broadcast receivingsystem according to the present invention may enhance the receivingperformance of the present invention. Most particularly, by estimatingand compensating a remaining carrier phase error from a channelequalized signal, the digital broadcast receiving system according tothe present invention may enhance the receiving performance of thepresent invention. FIG. 1 illustrates a block diagram of a channelequalizing device according to an embodiment of the present invention.Referring to FIG. 1, the channel equalizing device includes a firstfrequency domain converter 100, a channel estimator 110, a secondfrequency domain converter 121, a coefficient calculator 122, adistortion compensator 130, a time domain converter 140, a remainingcarrier phase error remover 150, a noise canceller (NC) 160, and adecision unit 170.

Herein, the first frequency domain converter 100 includes an overlapunit 101 overlapping inputted data, and a fast fourier transform (FFT)unit 102 converting the data outputted from the overlap unit 101 tofrequency domain data. The channel estimator 110 includes a CIRestimator 111 estimating a CIR from the inputted data, a phasecompensator 112 compensating the phase of the CIR estimated by the CIRestimator 111, and a linear interpolator 113 performing linearinterpolation on the CIR having its phase compensated. The secondfrequency domain converter 121 includes a FFT unit converting the CIRbeing outputted from the channel estimator 110 to a frequency domainCIR.

The time domain converter 140 includes an IFFT unit 141 converting thedata having the distortion compensated by the distortion compensator 130to time domain data, and a save unit 142 extracting only valid data fromthe data outputted from the IFFT unit 141. The remaining carrier phaseerror remover 150 includes an error compensator 151 removing theremaining carrier phase error included in the channel equalized data,and a remaining carrier phase error estimator 152 using the channelequalized data and the decision data of the decision unit 170 so as toestimate the remaining carrier phase error, thereby outputting theestimated error to the error compensator 151. Herein, any deviceperforming complex number multiplication may be used as the distortioncompensator 130 and the error compensator 151.

At this point, for example, since the received data correspond to datamodulated to VSB type data, 8-level scattered data exist only in thereal number element. Therefore, referring to FIG. 1, all of the signalsused in the noise canceller 160 and the decision unit 170 correspond toreal number (or in-phase) signals. However, in order to estimate andcompensate the remaining carrier phase error and the phase noise, bothreal number (in-phase) element and imaginary number (quadrature) elementare required. Therefore, the remaining carrier phase error remover 150receives and uses the quadrature element as well as the in-phaseelement. Generally, prior to performing the channel equalizationprocess, a demodulator (not shown) within the receiving system performsfrequency and phase recovery of the carrier. However, if a remainingcarrier phase error that is not sufficiently compensated is inputted tothe channel equalizer, the performance of the channel equalizer may bedeteriorated. Particularly, in a dynamic channel environment, theremaining carrier phase error may be larger than in a static channelenvironment due to the frequent and sudden channel changes. Eventually,this acts as an important factor that deteriorates the receivingperformance of the present invention.

Furthermore, a local oscillator (not shown) included in the receivingsystem should preferably include a single frequency element. However,the local oscillator actually includes the desired frequency elements aswell as other frequency elements. Such unwanted (or undesired) frequencyelements are referred to as phase noise of the local oscillator. Suchphase noise also deteriorates the receiving performance of the presentinvention. It is difficult to compensate such remaining carrier phaseerror and phase noise from the general channel equalizer. Therefore, thepresent invention may enhance the channel equaling performance byincluding a carrier recovery loop (i.e., a remaining carrier phase errorremover 150) in the channel equalizer, as shown in FIG. 1, in order toremove the remaining carrier phase error and the phase noise.

More specifically, the receiving data demodulated in FIG. 1 areoverlapped by the overlap unit 101 of the first frequency domainconverter 100 at a pre-determined overlapping ratio, which are thenoutputted to the FFT unit 102. The FFT unit 102 converts the overlappedtime domain data to overlapped frequency domain data through byprocessing the data with FFT. Then, the converted data are outputted tothe distortion compensator 130. The distortion compensator 130 performsa complex number multiplication on the overlapped frequency domain dataoutputted from the FFT unit 102 included in the first frequency domainconverter 100 and the equalization coefficient calculated from thecoefficient calculator 122, thereby compensating the channel distortionof the overlapped data outputted from the FFT unit 102. Thereafter, thecompensated data are outputted to the IFFT unit 141 of the time domainconverter 140. The IFFT unit 141 performs IFFT on the overlapped datahaving the channel distortion compensated, thereby converting theoverlapped data to time domain data, which are then outputted to theerror compensator 151 of the remaining carrier phase error remover 150.

The error compensator 151 multiplies a signal compensating the estimatedremaining carrier phase error and phase noise with the valid dataextracted from the time domain. Thus, the error compensator 151 removesthe remaining carrier phase error and phase noise included in the validdata. The data having the remaining carrier phase error compensated bythe error compensator 151 are outputted to the remaining carrier phaseerror estimator 152 in order to estimate the remaining carrier phaseerror and phase noise and, at the same time, outputted to the noisecanceller 160 in order to remove (or cancel) the noise.

The remaining carrier phase error estimator 152 uses the output data ofthe error compensator 151 and the decision data of the decision unit 170to estimate the remaining carrier phase error and phase noise.Thereafter, the remaining carrier phase error estimator 152 outputs asignal for compensating the estimated remaining carrier phase error andphase noise to the error compensator 151. In this embodiment of thepresent invention, an inverse number of the estimated remaining carrierphase error and phase noise is outputted as the signal for compensatingthe remaining carrier phase error and phase noise.

FIG. 2 illustrates a detailed block diagram of the remaining carrierphase error estimator 152 according to an embodiment of the presentinvention. Herein, the remaining carrier phase error estimator 152includes a phase error detector 211, a loop filter 212, a numericallycontrolled oscillator (NCO) 213, and a conjugator 214. Referring to FIG.2, the decision data, the output of the phase error detector 211, andthe output of the loop filter 212 are all real number signals. And, theoutput of the error compensator 151, the output of the NCO 213, and theoutput of the conjugator 214 are all complex number signals.

The phase error detector 211 receives the output data of the errorcompensator 151 and the decision data of the decision unit 170 in orderto estimate the remaining carrier phase error and phase noise. Then, thephase error detector 211 outputs the estimated remaining carrier phaseerror and phase noise to the loop filter 212. The loop filter 212 thenfilters the remaining carrier phase error and phase noise, therebyoutputting the filtered result to the NCO 213. The NCO 213 generates acosine wave corresponding to the filtered remaining carrier phase errorand phase noise, which is then outputted to the conjugator 214. Theconjugator 214 calculates the conjugate value of the cosine wavegenerated by the NCO 213. Thereafter, the calculated conjugate value isoutputted to the error compensator 151. At this point, the output dataof the conjugator 214 becomes the inverse number of the signalcompensating the remaining carrier phase error and phase noise. In otherwords, the output data of the conjugator 214 becomes the inverse numberof the remaining carrier phase error and phase noise.

The error compensator 151 performs complex number multiplication on theequalized data outputted from the time domain converter 140 and thesignal outputted from the conjugator 214 and compensating the remainingcarrier phase error and phase noise, thereby removing the remainingcarrier phase error and phase noise included in the equalized data.Meanwhile, the phase error detector 211 may estimate the remainingcarrier phase error and phase noise by using diverse methods andstructures. According to this embodiment of the present invention, theremaining carrier phase error and phase noise are estimated by using adecision-directed method.

If the remaining carrier phase error and phase noise are not included inthe channel-equalized data, the decision-directed phase error detectoraccording to the present invention uses the fact that only real numbervalues exist in the correlation values between the channel-equalizeddata and the decision data. More specifically, if the remaining carrierphase error and phase noise are not included, and when the input data ofthe phase error detector 211 are referred to as x_(i)+jx_(q), thecorrelation value between the input data of the phase error detector 211and the decision data may be obtained by using Equation 1 shown below:

E{(x _(i) +jx _(q))({circumflex over (x)} _(i) +j{circumflex over (x)}_(q))*}  Equation 1

At this point, there is no correlation between x_(i) and x_(q).Therefore, the correlation value between x_(i) and x_(q) is equal to 0.Accordingly, if the remaining carrier phase error and phase noise arenot included, only the real number values exist herein. However, if theremaining carrier phase error and phase noise are included, the realnumber element is shown in the imaginary number value, and the imaginarynumber element is shown in the real number value. Thus, in this case,the imaginary number element is shown in the correlation value.Therefore, it can be assumed that the imaginary number portion of thecorrelation value is in proportion with the remaining carrier phaseerror and phase noise. Accordingly, as shown in Equation 2 below, theimaginary number of the correlation value may be used as the remainingcarrier phase error and phase noise.

Phase Error=imag{(x _(i) +jx _(q))({circumflex over (x)} _(i)+j{circumflex over (x)} _(q))*}

Phase Error=x _(q) {circumflex over (x)} _(i) −x _(i) {circumflex over(x)} _(q)  Equation 2

FIG. 3 illustrates a block diagram of a phase error detector 211obtaining the remaining carrier phase error and phase noise. Herein, thephase error detector 211 includes a Hilbert converter 311, a complexnumber configurator 312, a conjugator 313, a multiplier 314, and a phaseerror output 315. More specifically, the Hilbert converter 311 createsan imaginary number decision data {circumflex over (x)}_(q) byperforming a Hilbert conversion on the decision value {circumflex over(x)}_(i) of the decision unit 170. The generated imaginary numberdecision value is then outputted to the complex number configurator 312.The complex number configurator 312 uses the decision data {circumflexover (x)}_(i) and {circumflex over (x)}_(q) to configure the complexnumber decision data {circumflex over (x)}_(i)+j{circumflex over(x)}_(q), which are then outputted to the conjugator 313. The conjugator313 conjugates the output of the complex number configurator 312,thereby outputting the conjugated value to the multiplier 314. Themultiplier 314 performs a complex number multiplication on the outputdata of the error compensator 151 and the output data {circumflex over(x)}_(i)−j{circumflex over (x)}_(q) of the conjugator 313, therebyobtaining the correlation between the output data x_(i)+jx_(q) of theerror compensator 151 and the decision value {circumflex over(x)}_(i)−j{circumflex over (x)}_(q) of the decision unit 170. Thecorrelation data obtained from the multiplier 314 are then inputted tothe phase error output 315. The phase error output 315 outputs theimaginary number portion x_(q){circumflex over (x)}_(i)−x_(i){circumflexover (x)}_(q) of the correlation data outputted from the multiplier 314as the remaining carrier phase error and phase noise.

The phase error detector shown in FIG. 3 is an example of a plurality ofphase error detecting methods. Therefore, other types of phase errordetectors may be used in the present invention. Therefore, the presentinvention is not limited only to the examples and embodiments presentedin the description of the present invention. Furthermore, according toanother embodiment of the present invention, at least 2 phase errordetectors are combined so as to detect the remaining carrier phase errorand phase noise. Accordingly, the output of the remaining carrier phaseerror remover 150 having the detected remaining carrier phase error andphase noise removed as described above, is configured of an addition ofthe original (or initial) signal having the channel equalization, theremaining carrier phase error and phase noise, and the signalcorresponding to a white noise being amplified to a colored noise duringthe channel equalization.

Therefore, the noise canceller 160 receives the output data of theremaining carrier phase error remover 150 and the decision data of thedecision unit 170, thereby estimating the colored noise. Then, the noisecanceller 160 subtracts the estimated colored noise from the data havingthe remaining carrier phase error and phase noise removed therefrom,thereby removing the noise amplified during the equalization process.The data having the noise removed (or cancelled) by the noise canceller160 are outputted for the data decoding process and, at the same time,outputted to the decision unit 170.

The decision unit 170 selects one of a plurality of pre-determineddecision data sets (e.g., B decision data sets) that is most approximateto the output data of the noise canceller 160, thereby outputting theselected data to the remaining carrier phase error estimator 152 and thenoise canceller 160. Meanwhile, the received data are inputted to theoverlap unit 101 of the first frequency domain converter 100 included inthe channel equalizer and, at the same time, inputted to the CIRestimator 111 of the channel estimator 110. The CIR estimator 111 uses atraining sequence, for example, data being inputted during the knowndata section and the known data in order to estimate the CIR, therebyoutputting the estimated CIR to the phase compensator 112. Herein, theknown data correspond to reference known data generated during the knowndata section by the receiving system in accordance with an agreementbetween the receiving system and the transmitting system.

Furthermore, in this embodiment of the present invention, the CIRestimator 111 estimates the CIR by using the least square (LS) method.The LS estimation method calculates a cross correlation value p betweenthe known data that have passed through the channel during the knowndata section and the known data that are already known by the receivingend. Then, a cross correlation matrix R of the known data is calculated.Subsequently, a matrix operation is performed on R⁻¹·p so that the crosscorrelation portion within the cross correlation value p between thereceived data and the initial known data, thereby estimating the CIR ofthe transmission channel.

The phase compensator 112 compensates the phase change of the estimatedCIR. Then, the phase compensator 112 outputs the compensated CIR to thelinear interpolator 113. At this point, the phase compensator 112 maycompensate the phase change of the estimated CIR by using a maximumlikelihood method. More specifically, the remaining carrier phase errorand phase noise that are included in the demodulated received data and,therefore, being inputted change the phase of the CIR estimated by theCIR estimator 111 at a cycle period of one known data sequence. At thispoint, if the phase change of the inputted CIR, which is to be used forthe linear interpolation process, is not performed in a linear form dueto a high rate of the phase change, the channel equalizing performanceof the present invention may be deteriorated when the channel iscompensated by calculating the equalization coefficient from the CIR,which is estimated by a linear interpolation method.

Therefore, the present invention removes (or cancels) the amount ofphase change of the CIR estimated by the CIR estimator 111 so that thedistortion compensator 130 allows the remaining carrier phase error andphase noise to bypass the distortion compensator 130 without beingcompensated. Accordingly, the remaining carrier phase error and phasenoise are compensated by the remaining carrier phase error remover 150.For this, the present invention removes (or cancels) the amount of phasechange of the CIR estimated by the phase compensator 112 by using amaximum likelihood method. The basic idea of the maximum likelihoodmethod relates to estimating a phase element mutually (or commonly)existing in all CIR elements, then to multiply the estimated CIR with aninverse number of the mutual (or common) phase element, so that thechannel equalizer, and most particularly, the distortion compensator 130does not compensate the mutual phase element.

More specifically, when the mutual phase element is referred to as θ,the phase of the newly estimated CIR is rotated by θ as compared to thepreviously estimated CIR. When the CIR of a point t is referred to ash_(i)(t), the maximum likelihood phase compensation method obtains aphase θ_(ML) corresponding to when h_(i)(t) is rotated by θ, the squaredvalue of the difference between the CIR of h_(i)(t) and the CIR ofh_(i)(t+1), i.e., the CIR of a point (t+1), becomes a minimum value.Herein, when i represents a tap of the estimated CTR, and when Nrepresents a number of taps of the CIR being estimated by the CIRestimator 111, the value of θ_(ML) is equal to or greater than 0 andequal to or less than N−1. This value may be calculated by usingEquation 3 shown below:

$\begin{matrix}{\theta_{ML} = {\min\limits_{\theta}{\sum\limits_{i = 0}^{N - 1}{{{{h_{i}(t)}^{j\theta}} - {h_{i}\left( {t + 1} \right)}}}^{2}}}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

Herein, in light of the maximum likelihood method, the mutual phaseelement θ_(ML) is equal to the value of θ, when the right side ofEquation 3 being differentiated with respect to θ is equal to 0. Theabove-described condition is shown in Equation 4 below:

$\begin{matrix}{{\frac{}{\theta}{\sum\limits_{i = 0}^{N - 1}{{{{h_{i}(t)}^{j\theta}} - {h_{i}\left( {t + 1} \right)}}}^{2}}} = {{\frac{}{\theta}{\sum\limits_{i = 0}^{N - 1}{\left( {{{h_{i}(t)}^{j\theta}} - {h_{i}\left( {t + 1} \right)}} \right)\left( {{{h_{i}(t)}^{j\theta}} - {h_{i}\left( {t + 1} \right)}} \right)^{*}}}} = {{\frac{}{\theta}{\sum\limits_{i = 0}^{N - 1}\begin{Bmatrix}{{{h_{i}(t)}}^{2} + {{h_{i + 1}(t)}}^{2} -} \\{{{h_{i}(t)}{h_{i}^{*}\left( {t + 1} \right)}^{j\theta}} - {{h_{i}^{*}(t)}{h_{i}\left( {t + 1} \right)}^{- {j\theta}}}}\end{Bmatrix}}} = {{\sum\limits_{i = 0}^{N - 1}\left\{ {{j\; {h_{i}^{*}(t)}{h_{i}\left( {t + 1} \right)}^{- {j\theta}}} - {j\; {h_{i}^{*}(t)}{h_{i}\left( {t + 1} \right)}^{j\theta}}} \right\}} = {{j{\sum\limits_{i = 0}^{N - 1}{2{Im}\left\{ {{h_{i}^{*}(t)}{h_{i}\left( {t + 1} \right)}^{- {j\theta}}} \right\}}}} = 0}}}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

The above Equation 4 may be simplified as shown in Equation 5 below:

$\begin{matrix}{{{{Im}\left\{ {^{- {j\theta}}{\sum\limits_{i = 0}^{N - 1}\left\{ {{h_{i}^{*}(t)}{h_{i}\left( {t + 1} \right)}} \right\}}} \right\}} = 0}{\theta_{ML} = {\arg \left( {\sum\limits_{i = 0}^{N - 1}{{h_{i}^{*}(t)}{h_{i}\left( {t + 1} \right)}}} \right)}}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

More specifically, Equation 5 corresponds to the θ_(ML) value that is tobe estimated by the argument of the correlation value between h_(i)(t)and h_(i)(t+1).

FIG. 4 illustrates a phase compensator according to an embodiment of thepresent invention, wherein the mutual phase element θ_(ML) is calculatedas described above, and wherein the estimated phase element iscompensated at the estimated CIR. Referring to FIG. 4, the phasecompensator includes a correlation calculator 410, a phase changeestimator 420, a compensation signal generator 430, and a multiplier440. The correlation calculator 410 includes a first N symbol buffer411, an N symbol delay 412, a second N symbol buffer 413, a conjugator414, and a multiplier 415. More specifically, the first N symbol buffer411 included in the correlation calculator 410 is capable of storing thedata being inputted from the CIR estimator 111 in symbol units to amaximum limit of N number of symbols. The symbol data being temporarilystored in the first N symbol buffer 411 are then inputted to themultiplier 415 included in the correlation calculator 410 and to themultiplier 440.

At the same time, the symbol data being outputted from the CIR estimator111 are delayed by N symbols from the N symbol delay 412. Then, thedelayed symbol data pass through the second N symbol buffer 413 andinputted to the conjugator 414, so as to be conjugated and then inputtedto the multiplier 415. The multiplier 415 multiplies the output of thefirst N symbol buffer 411 and the output of the conjugator 414. Then,the multiplier 415 outputs the multiplied result to an accumulator 421included in the phase change estimator 420. More specifically, thecorrelation calculator 410 calculates a correlation between a currentCIR h_(i)(t+1) having the length of N and a previous CIR h_(i)(i) alsohaving the length of N. Then, the correlation calculator 410 outputs thecalculated correlation value to the accumulator 421 of the phase changeestimator 420.

The accumulator 421 accumulates the correlation values outputted fromthe multiplier 415 during an N symbol period. Then, the accumulator 421outputs the accumulated value to the phase detector 422. The phasedetector 422 then calculates a mutual phase element θ_(ML) from theoutput of the accumulator 421 as shown in the above-described Equation4. Thereafter, the calculated θ_(ML) value is outputted to thecompensation signal generator 430. The compensation signal generator 430outputs a complex signal e^(−jθ) ^(ML) having a phase opposite to thatof the detected phase as the phase compensation signal to the multiplier440. The multiplier 440 multiplies the current CIR h_(i)(t+1) beingoutputted from the first N symbol buffer 411 with the phase compensationsignal e^(−jθ) ^(ML) , thereby removing the amount of phase change ofthe estimated CIR.

As described above, the phase compensator 112 using the maximumlikelihood method calculates a phase element corresponding to thecorrelation value between the inputted CIR and the previous CIR beingdelayed by N symbols. Thereafter, the phase compensator 112 generates aphase compensation signal having a phase opposite to that of the phaseelement calculated as described above. Subsequently, the phasecompensator 112 multiplies the generated phase compensation signal tothe estimated CIR, thereby removing the amount of phase change of theestimated CIR. The CIR having the phase change compensated is inputtedto the linear interpolator 113. The linear interpolator 113 linearlyinterpolates the CIRs having the phase changes compensated to the secondfrequency domain converter 121.

More specifically, the linear interpolator 113 receives the CIR havingthe phase change compensated from the phase compensator 112.Accordingly, during the known data section, the linear interpolator 113outputs the received CIR, and during the data section in-between knowndata, the CIR is interpolated in accordance with a pre-determinedinterpolating method. Thereafter, the interpolated CIR is outputted. Inthis embodiment of the present invention, a linear interpolation method,which is one of the many pre-determined interpolating methods, is usedto interpolate the CIRs. Herein, the present invention may also useother interpolation methods. Therefore, the present invention is notlimited only to the examples given in the description of the presentinvention.

The second frequency domain converter 121 performs FFT on the CIR beingoutputted from the linear interpolator 113, thereby converting the CIRto a frequency domain CIR. Then, the second frequency domain converter121 outputs the converted CIR to the coefficient calculator 122. Thecoefficient calculator 122 uses the frequency domain CIR being outputtedfrom the second frequency domain converter 121 to calculate theequalization coefficient. Then, the coefficient calculator 122 outputsthe calculated coefficient to the distortion compensator 130. Herein,for example, the coefficient calculator 122 calculates a channelequalization coefficient of the frequency domain that can provideminimum mean square error (MMSE) from the CIR of the frequency domain,which is outputted to the distortion compensator 130. The distortioncompensator 130 performs a complex number multiplication on theoverlapped data of the frequency domain being outputted from the FFTunit 102 of the first frequency domain converter 100 and theequalization coefficient calculated by the coefficient calculator 122,thereby compensating the channel distortion of the overlapped data beingoutputted from the FFT unit 102.

FIG. 5 illustrates a block diagram of a demodulating unit of a digitalbroadcast receiving system according to an embodiment of the presentinvention. The digital broadcast receiving system of FIG. 5 is merely anexample given to facilitate the understanding of the present invention.Therefore, any receiving system adopting a channel equalizing device asdescribed above may be applied in the present invention. Therefore, thepresent invention is not limited to the examples set forth in thedescription of the present invention.

Referring to FIG. 5, the demodulating unit of the digital broadcastreceiving system includes a demodulator 501, an equalizer 502, a knowndata detector 503, an enhanced decoder 504, a data deinterleaver 505, aRS decoder 506, a data derandomizer 507, a data deformatter 508, and anenhanced data processor 509. More specifically, an intermediatefrequency (IF) signal of a particular channel that is tuned by a tuneris inputted to the demodulator 501 and the known data detector 503. Thedemodulator 501 performs self gain control, carrier recovery, and timingrecovery processes on the inputted IF signal, thereby modifying the IFsignal to a baseband signal. Then, the demodulator 501 outputs the newlycreated baseband signal to the equalizer 502 and the known data detector503. The equalizer 502 compensates the distortion of the channelincluded in the demodulated signal and then outputs theerror-compensated signal to the known data detector 503.

At this point, the known data detector 503 detects the known sequenceplace inserted by the transmitting end from the input/output data of thedemodulator 501 (i.e., the data prior to the demodulation or the dataafter the modulation). Thereafter, the place information along with theknown data sequence, which is generated from the detected place, isoutputted to the demodulator 501, the equalizer 502, and the enhanceddecoder 504. Also, the known data detector 503 outputs a set ofinformation to the enhanced decoder 504. This set of information isoutputted to the enhanced data decoder 504, so as to allow the enhanceddecoder 504 of the receiving system to identify the enhanced data thatare processed with additional encoding from the transmitting system andthe main data that are not processed with additional encoding.

The demodulator 501 uses the known data during the timing and/or carrierrecovery, thereby enhancing the demodulating performance. Similarly, theequalizer 502 uses the known data sequence, thereby enhancing theequalizing quality. As shown in FIG. 1 to FIG. 4, the equalizer 502 usesthe known data to estimate the CIR, thereby performing phase changecompensation and linear interpolation processes on the estimated CIR.Thereafter, the processed data are used to compensate the distortionwithin the channel included in the demodulated data. Furthermore, theequalizer 502 uses the equalized data and the decision data of theequalized data so as to estimate the remaining carrier phase error andphase noise, thereby removing (or canceling) the estimated remainingcarrier phase error and phase noise from the equalized data.

Accordingly, the output data of the equalizer 502 are inputted to theenhanced decoder 504. Herein, if the data that are inputted to theenhanced decoder 504 from the equalizer 502 correspond to the enhanceddata being processed with both additional encoding and trellis encodingby the transmitting system, the enhanced decoder 504 performs trellisdecoding and additional decoding processes as inverse processes of thetransmitting system. Alternatively, if the data that are inputted to theenhanced decoder 504 from the equalizer 502 correspond to the main databeing processed only with the trellis encoding process and not theadditional encoding process, then only the trellis decoding process isperformed.

If the inputted data correspond to the main data or known data, theenhanced decoder 504 either performs Viterbi decoding on the input data,or performs hard decision on a soft decision value, thereby outputtingthe processed data (or result). In additional, since the RS parity bytesand MPEG header bytes, which have been inserted to the enhanced datapacket by the transmitting system, are considered as main data by thetransmitting system, the RS parity bytes and MPEG header bytes are notprocessed with any additional encoding processes. Therefore, either aViterbi decoding process is performed on the RS parity bytes and MPEGheader bytes, or a hard decision process is performed on thecorresponding soft decision value. Thus, the processed result isoutputted.

Meanwhile, if the inputted data correspond to the enhanced data, theenhanced decoder 504 may either output a hard decision value withrespect to the inputted enhanced data, or output a soft decision value.If the soft decision value is outputted, the performance of theadditional error correction decoding process performed on the enhanceddata by the enhanced data processor 509 at a later block may beenhanced. Therefore, an example of the enhanced decoder 504 outputting asoft decision value on the enhanced data will now be described indetail.

Herein, the output of the enhanced decoder 504 is inputted to the datadeinterleaver 505. The data deinterleaver 505 performs an inverseprocess of the data interleaver included in the transmitting system.Then, the data deinterleaver 505 outputs the deinterleaved data to theRS decoder 506. Furthermore, the decoded result of the enhanced decoder504 may be fed-back to the equalizer 502, thereby enhancing theequalizing performance. If the received packet corresponds to a maindata packet, the RS decoder 506 performs systematic RS decoding. If thereceived packet corresponds to an enhanced data packet, the RS decoder506 performs either systematic RS decoding or non-systematic RSdecoding. More specifically, if the transmitting system performedsystematic RS encoding on the enhanced data packet, the RS decoder 506performs systematic RS decoding on the received packet. On the otherhand, if the transmitting system performed non-systematic RS encoding onthe enhanced data packet, the RS decoder 506 performs non-systematic RSdecoding on the received packet.

The output data of the RS decoder 506 are then inputted to the dataderandomizer 507. The data derandomizer 507 receives the data outputtedfrom the RS decoder 506 and generates a pseudo random data byteidentical to that of the randomizer included in the digital broadcasttransmitting system (or DTV transmitter). Thereafter, the dataderandomizer 507 performs a bitwise exclusive OR (XOR) operation betweenthe generated pseudo random data byte and the data packet data packetoutputted from the RS decoder 506, thereby inserting the MPEGsynchronization bytes to the beginning of each packet so as to outputthe data in 188-byte packet units. The output of the data derandomizer507 is inputted to a main MPEG decoder (not shown) and to the datadeformatter 508 at the same time. The main MPEG decoder performsdecoding only on the data packet corresponding to the main MPEG. Herein,since the enhanced data packet includes a PID that is not used by theconventional receiving system, a null PID, or a reserved PID, theenhanced data packet is not used by the main MPEG decoder for decodingand, therefore, disregarded.

However, it is difficult to perform a bitwise exclusive OR (XOR)operation between the soft decision value of the enhanced data and thepseudo random bit. Therefore, as described above, depending upon thecode of the soft decision value, a hard decision is performed on thedata that ate to be outputted to the main MPEG decoder. Then, an XORoperation is performed between the pseudo random bit and the harddecided data, which are then outputted. More specifically, if the codeof the soft decision value is a positive number, the hard decision valueis equal to ‘1’. And, if the code of the soft decision value is anegative number, the hard decision value is equal to ‘0’. Thereafter, anXOR operation is performed between the pseudo random bit and any one ofthe hard decided values.

However, as described above, a soft decision is more efficient in theenhanced data processor 509 in order to enhance the performance whendecoding the error correction code. Therefore, the data derandomizer 507creates a separate output data with respect to the enhanced data, whichare then outputted to the data deformatter 508. For example, when thepseudo random bit is equal to ‘1’, the data derandomizer 507 changes thecode of the soft decision value and then outputs the changed code. Onthe other hand, if the pseudo random bit is equal to ‘0’, the dataderandomizer 507 outputs the soft decision value without any change inthe code.

As described above, if the pseudo random bit is equal to ‘1’, the codeof the soft decision value is changed because, when an XOR operation isperformed between the pseudo random bit and the input data in therandomizer of the transmitting system, and when the pseudo random bit isequal to ‘1’, the code of the output data bit becomes the opposite ofthe input data (i.e., 0 XOR 1=1 and 1 XOR 0=0). More specifically, ifthe pseudo random bit generated from the data derandomizer 507 is equalto ‘1’, and when an XOR operation is performed on the hard decisionvalue of the enhanced data bit, the XOR-operated value becomes theopposite value of the hard decision value. Therefore, when the softdecision value is outputted, a code opposite to that of the softdecision value is outputted.

If the inputted data correspond to the main data packet, the datadeformatter 508 does not output the inputted data to the enhanced dataprocessor 509. In addition, if the inputted data correspond to theenhanced data packet, the data deformatter 508 removes the MPEG headerbytes, the known data, and so on, which are included in the enhanceddata packet. Then, the data deformatter 508 outputs the processed datato the enhanced data processor 509. Then, the enhanced data processor509 further processes the input data with a null bit removing process,so as to remove all null data used for the byte expansion of theinputted enhanced data, a deinterleaving process and an error correctiondecoding process. Thereafter, the enhanced data processor 509 outputsthe processed enhanced data as the final enhanced data.

FIG. 6 illustrates a block diagram showing the structure of a digitalbroadcast transmitting system according to an embodiment of the presentinvention. The digital broadcast (or DTV) transmitting system includes apre-processor 610, a packet multiplexer 621, a data randomizer 622, aReed-Solomon (RS) encoder/non-systematic RS encoder 623, a datainterleaver 624, a parity byte replacer 625, a non-systematic RS encoder626, a frame multiplexer 628, and a transmitting unit 630. Thepre-processor 610 includes an enhanced data randomizer 611, a RS frameencoder 612, a block processor 613, a group formatter 614, a datadeinterleaver 615, and a packet formatter 616.

In the present invention having the above-described structure, main dataare inputted to the packet multiplexer 621. Enhanced data are inputtedto the enhanced data randomizer 611 of the pre-processor 610, wherein anadditional coding process is performed so that the present invention canrespond swiftly and appropriately against noise and change in channel.The enhanced data randomizer 611 randomizes the received enhanced dataand outputs the randomized enhanced data to the RS frame encoder 612. Atthis point, by having the enhanced data randomizer 611 perform therandomizing process on the enhanced data, the randomizing process on theenhanced data by the data randomizer 622 in a later process may beomitted. Either the randomizer of the conventional broadcast system maybe used as the randomizer for randomizing the enhanced data, or anyother type of randomizer may be used herein.

The RS frame encoder 612 receives the randomized enhanced data andperforms at least one of an error correction coding process and an errordetection coding process on the received data. Accordingly, by providingrobustness to the enhanced data, the data can scatter group error thatmay occur due to a change in the frequency environment. Thus, the datacan respond appropriately to the frequency environment which is verypoor and liable to change. The RS frame multiplexer 612 also includes aprocess of mixing in row units many sets of enhanced data each having apre-determined size. By performing an error correction coding process onthe inputted enhanced data, the RS frame encoder 612 adds data requiredfor the error correction and, then, performs an error detection codingprocess, thereby adding data required for the error detection process.The error correction coding uses the RS coding method, and the errordetection coding uses the cyclic redundancy check (CRC) coding method.When performing the RS coding process, parity data required for theerror correction are generated. And, when performing the CRC codingprocess, CRC data required for the error detection are generated.

The RS frame encoder 612 performs CRC coding on the RS coded enhanceddata in order to create the CRC code. The CRC code that is generated bythe CRC coding process may be used to indicate whether the enhanced datahave been damaged by an error while being transmitted through thechannel. The present invention may adopt other types of error detectioncoding methods, apart from the CRC coding method, and may also use theerror correction coding method so as to enhance the overall errorcorrection ability of the receiving system. For example, assuming thatthe size of one RS frame is 187 (column)*N (row) bytes, that(235,187)-RS coding process is performed on each column within the RSframe, and that a CRC coding process using a 2-byte (i.e., 16-bit) CRCchecksum, then a RS frame having the size of 187*N bytes is expanded toa RS frame of 235*(N+2) bytes. The RS frame expanded by the RS frameencoder 612 is inputted to the block processor 613. The block processor613 codes the RS-coded and CRC-coded enhanced data at a coding rate ofM1/N1. Then, the block processor 613 outputs the M1/N1-rate codedenhanced data to the group formatter 614. In order to do so, the blockprocessor 613 identifies the block data bytes being inputted from the RSframe encoder 612 as bits.

The block processor 613 may receive supplemental information data suchas signaling information, which include information on the system, andidentifies the supplemental information data bytes as data bits. Herein,the supplemental information data, such as the signaling information,may equally pass through the enhanced data randomizer 611 and the RSframe encoder 612 so as to be inputted to the block processor 613.Alternatively, the supplemental information data may be directlyinputted to the block processor 613 without passing through the enhanceddata randomizer 611 and the RS frame encoder 612. The signalinginformation corresponds to information required for receiving andprocessing data included in the data group in the receiving system. Suchsignaling information includes data group information, multiplexinginformation, and burst information.

As a M1/N1-rate encoder, the block processor 613 codes the inputted dataat a coding rate of M1/N1 and then outputs the M1/N1-rate coded data.For example, if 1 bit of the input data is coded to 2 bits andoutputted, then M1 is equal to 1 and N1 is equal to 2 (i.e., M1=1 andN1=2). Alternatively, if 1 bit of the input data is coded to 4 bits andoutputted, then M1 is equal to 1 and N1 is equal to 4 (i.e., M1=1 andN1=4). As an example of the present invention, it is assumed that theblock processor 613 performs a coding process at a coding rate of ½(also referred to as a ½-rate coding process) or a coding process at acoding rate of ¼ (also referred to as a ¼-rate coding process). Morespecifically, the block processor 613 codes the received enhanced dataand supplemental information data, such as the signaling information, ateither a coding rate of ½ or a coding rate of ¼. Thereafter, thesupplemental information data, such as the signaling information, areidentified and processed as enhanced data.

Since the ¼-rate coding process has a higher coding rate than the ½-ratecoding process, greater error correction ability may be provided.Therefore, in a later process, by allocating the ¼-rate coded data in anarea with deficient receiving performance within the group formatter614, and by allocating the ½-rate coded data in an area with excellentreceiving performance, the difference in the overall performance may bereduced. More specifically, in case of performing the ½-rate codingprocess, the block processor 613 receives 1 bit and codes the received 1bit to bits (i.e., 1 symbol). Then, the block processor 613 outputs theprocessed 2 bits (or 1 symbol). On the other hand, in case of performingthe ¼-rate coding process, the block processor 613 receives 1 bit andcodes the received 1 bit to 4 bits (i.e., 2 symbols). Then, the blockprocessor 613 outputs the processed 4 bits (or 2 symbols). Additionally,the block processor 613 performs a block interleaving process in symbolunits on the symbol-coded data. Subsequently, the block processor 613converts to bytes the data symbols that are block-interleaved and havethe order rearranged.

The group formatter 614 inserts the enhanced data outputted from theblock processor 613 (herein, the enhanced data may include supplementalinformation data such as signaling information including transmissioninformation) in a corresponding area within the data group, which isconfigured according to a pre-defined rule. Furthermore, in relationwith the data deinterleaving process, various types of places holders orknown data are also inserted in corresponding areas within the datagroup. At this point, the data group may be described by at least onehierarchical area. Herein, the data allocated to the each area may varydepending upon the characteristic of each hierarchical area.Additionally, each data group may be configured to include a fieldsynchronization signal.

In another example given in the present invention, a data group isdivided into A, B, and C regions in a data configuration prior to datadeinterleaving.

FIG. 7 illustrates an alignment of data before being data deinterleavedand identified, and FIG. 8 illustrates an alignment of data after beingdata deinterleaved and identified. More specifically, a data structureidentical to that shown in FIG. 7 is transmitted to a receiving system.Also, the data group configured to have the same structure as the datastructure shown in FIG. 7 is inputted to the data deinterleaver 615.

As described above, FIG. 7 illustrates a data structure prior to datadeinterleaving that is divided into 3 regions, such as region A, regionB, and region C. Also, in the present invention, each of the regions Ato C is further divided into a plurality of regions. Referring to FIG.7, region A is divided into 5 regions (A1 to A5), region B is dividedinto 2 regions (B1 and B2), and region C is divided into 3 regions (C1to C3). Herein, regions A to C are identified as regions having similarreceiving performances within the data group. Herein, the type ofenhanced data, which are inputted, may also vary depending upon thecharacteristic of each region.

In the example of the present invention, the data structure is dividedinto regions A to C based upon the level of interference of the maindata. Herein, the data group is divided into a plurality of regions tobe used for different purposes. More specifically, a region of the maindata having no interference or a very low interference level may beconsidered to have a more resistant (or stronger) receiving performanceas compared to regions having higher interference levels. Additionally,when using a system inserting and transmitting known data in the datagroup, and when consecutively long known data are to be periodicallyinserted in the enhanced data, the known data having a predeterminedlength may be periodically inserted in the region having no interferencefrom the main data (e.g., region A). However, due to interference fromthe main data, it is difficult to periodically insert known data andalso to insert consecutively long known data to a region havinginterference from the main data (e.g., region B and region C).

Hereinafter, examples of allocating data to region A (A1 to A5), regionB (B1 and B2), and region C (C1 to C3) will now be described in detailwith reference to FIG. 7. The data group size, the number ofhierarchically divided regions within the data group and the size ofeach region, and the number of enhanced data bytes that can be insertedin each hierarchically divided region of FIG. 7 are merely examplesgiven to facilitate the understanding of the present invention. Herein,the group formatter 614 creates a data group including places in whichfield synchronization bytes are to be inserted, so as to create the datagroup that will hereinafter be described in detail.

More specifically, region A is a region within the data group in which along known data sequence may be periodically inserted, and in whichincludes regions wherein the main data are not mixed (e.g., A1 to A5).Also, region A includes a region (e.g., A1) located between a fieldsynchronization region and the region in which the first known datasequence is to be inserted. The field synchronization region has thelength of one segment (i.e., 832 symbols) existing in an ATSC system.

For example, referring to FIG. 7, 2428 bytes of the enhanced data may beinserted in region A1, 2580 bytes may be inserted in region A2, 2772bytes may be inserted in region A3, 2472 bytes may be inserted in regionA4, and 2772 bytes may be inserted in region A5. Herein, trellisinitialization data or known data, MPEG header, and RS parity are notincluded in the enhanced data. As described above, when region Aincludes a known data sequence at both ends, the receiving system useschannel information that can obtain known data or field synchronizationdata, so as to perform equalization, thereby providing enforcedequalization performance.

Also, region B includes a region located within B segments at thebeginning of a field synchronization region within the data group(chronologically placed before region A1) (e.g., region B1), and aregion located within 8 segments behind the very last known datasequence which is inserted in the data group (e.g., region B2). Forexample, 630 bytes of the enhanced data may be inserted in the regionB1, and 1350 bytes may be inserted in region B2. Similarly, trellisinitialization data or known data, MPEG header, and RS parity are notincluded in the enhanced data. In case of region B, the receiving systemmay perform equalization by using channel information obtained from thefield synchronization section. Alternatively, the receiving system mayalso perform equalization by using channel information that may beobtained from the last known data sequence, thereby enabling the systemto respond to the channel changes.

Region C includes a region located within 30 segments including andpreceding the 9^(th) segment of the field synchronization region(chronologically located before region A) (e.g., region C1), a regionlocated within 12 segments including and following the 9^(th) segment ofthe very last known data sequence within the data group (chronologicallylocated after region A) (e.g., region C2), and a region located in 32segments after the region C2 (e.g., region C3). For example, 1272 bytesof the enhanced data may be inserted in the region C1, 1560 bytes may beinserted in region C2, and 1312 bytes may be inserted in region C3.Similarly, trellis initialization data or known data, MPEG header, andRS parity are not included in the enhanced data. Herein, region C (e.g.,region C1) is located chronologically earlier than (or before) region A.

Since region C (e.g., region C1) is located further apart from the fieldsynchronization region which corresponds to the closest known dataregion, the receiving system may use the channel information obtainedfrom the field synchronization data when performing channelequalization. Alternatively, the receiving system may also use the mostrecent channel information of a previous data group. Furthermore, inregion C (e.g., region C2 and region C3) located before region A, thereceiving system may use the channel information obtained from the lastknown data sequence to perform equalization. However, when the channelsare subject to fast and frequent changes, the equalization may not beperformed perfectly. Therefore, the equalization performance of region Cmay be deteriorated as compared to that of region B.

When it is assumed that the data group is allocated with a plurality ofhierarchically divided regions, as described above, the block processor613 may encode the enhanced data, which are to be inserted to eachregion based upon the characteristic of each hierarchical region, at adifferent coding rate. For example, the block processor 613 may encodethe enhanced data, which are to be inserted in regions A1 to A5 ofregion A, at a coding rate of ½. Then, the group formatter 614 mayinsert the ½-rate encoded enhanced data to regions A1 to A5.

The block processor 613 may encode the enhanced data, which are to beinserted in regions B1 and B2 of region B, at a coding rate of ¼ havinghigher error correction ability as compared to the ½-coding rate. Then,the group formatter 614 inserts the ¼-rate coded enhanced data in regionB1 and region B2. Furthermore, the block processor 613 may encode theenhanced data, which are to be inserted in regions C1 to C3 of region C,at a coding rate of ¼ or a coding rate having higher error correctionability than the ¼-coding rate. Then, the group formatter 614 may eitherinsert the encoded enhanced data to regions C1 to C3, as describedabove, or leave the data in a reserved region for future usage.

In addition, the group formatter 614 also inserts supplemental data,such as signaling information that notifies the overall transmissioninformation, other than the enhanced data in the data group. Also, apartfrom the encoded enhanced data outputted from the block processor 613,the group formatter 614 also inserts MPEG header place holders,non-systematic RS parity place holders, main data place holders, whichare related to data deinterleaving in a later process, as shown in FIG.7. Herein, the main data place holders are inserted because the enhanceddata bytes and the main data bytes are alternately mixed with oneanother in regions B and C based upon the input of the datadeinterleaver, as shown in FIG. 7. For example, based upon the dataoutputted after data deinterleaving, the place holder for the MPEGheader may be allocated at the very beginning of each packet.

Furthermore, the group formatter 614 either inserts known data generatedin accordance with a pre-determined method or inserts known data placeholders for inserting the known data in a later process. Additionally,place holders for initializing the trellis encoder 627 are also insertedin the corresponding regions. For example, the initialization data placeholders may be inserted in the beginning of the known data sequence.Herein, the size of the enhanced data that can be inserted in a datagroup may vary in accordance with the sizes of the trellisinitialization place holders or known data (or known data placeholders), MPEG header place holders, and RS parity place holders.

The output of the group formatter 614 is inputted to the datadeinterleaver 615. And, the data deinterleaver 615 deinterleaves data byperforming an inverse process of the data interleaver on the data andplace holders within the data group, which are then outputted to thepacket formatter 616. More specifically, when the data and place holderswithin the data group configured, as shown in FIG. 7, are deinterleavedby the data deinterleaver 615, the data group being outputted to thepacket formatter 616 is configured to have the structure shown in FIG.8.

Among the data deinterleaved and inputted, the packet formatter 616removes the main data place holder and RS parity place holder that wereallocated for the deinterleaving process from the inputted deinterleaveddata. Thereafter, the remaining portion of the corresponding data isgrouped, and 4 bytes of MPEG header are inserted therein. The 4-byteMPEG header is configured of a 1-byte MPEG synchronization byte added tothe 3-byte MPEG header place holder.

When the group formatter 614 inserts the known data place holder, thepacket formatter 616 may either insert actual known data in the knowndata place holder or output the known data place holder without anychange or modification for a replacement insertion in a later process.Afterwards, the packet formatter 616 divides the data within theabove-described packet-formatted data group into 188-byte unit enhanceddata packets (i.e., MPEG TS packets), which are then provided to thepacket multiplexer 621. The packet multiplexer 621 multiplexes the188-byte unit enhanced data packet and main data packet outputted fromthe packet formatter 616 according to a pre-defined multiplexing method.Subsequently, the multiplexed data packets are outputted to the datarandomizer 622. The multiplexing method may be modified or altered inaccordance with diverse variables of the system design.

As an example of the multiplexing method of the packet multiplexer 621,the enhanced data burst section and the main data section may beidentified along a time axis (or a chronological axis) and may bealternately repeated. At this point, the enhanced data burst section maytransmit at least one data group, and the main data section may transmitonly the main data. The enhanced data burst section may also transmitthe main data. If the enhanced data are outputted in a burst structure,as described above, the receiving system receiving only the enhanceddata may turn the power on only during the burst section so as toreceive the enhanced data, and may turn the power off during the maindata section in which main data are transmitted, so as to prevent themain data from being received, thereby reducing the power consumption ofthe receiving system.

When the data being inputted correspond to the main data packet, thedata randomizer 622 performs the same randomizing process of theconventional randomizer. More specifically, the MPEG synchronizationbyte included in the main data packet is discarded and a pseudo randombyte generated from the remaining 187 bytes is used so as to randomizethe data. Thereafter, the randomized data are outputted to the RSencoder/non-systematic RS encoder 623. However, when the inputted datacorrespond to the enhanced data packet, the MPEG synchronization byte ofthe 4-byte MPEG header included in the enhanced data packet isdiscarded, and data randomizing is performed only on the remaining3-byte MPEG header. Randomizing is not performed on the remainingportion of the enhanced data. Instead, the remaining portion of theenhanced data is outputted to the RS encoder/non-systematic RS encoder623. This is because the randomizing process has already been performedon the enhanced data by the enhanced data randomizer 611 in an earlierprocess. Herein, a data randomizing process may or may not be performedon the known data (or known data place holder) and the initializationdata place holder included in the enhanced data packet.

The RS encoder/non-systematic RS encoder 623 RS-codes the datarandomized by the data randomizer 622 or the data bypassing the datarandomizer 622. Then, the RS encoder/non-systematic RS encoder 623 addsa 20-byte RS parity to the coded data, thereby outputting theRS-parity-added data to the data interleaver 624. At this point, if theinputted data correspond to the main data packet, the RSencoder/non-systematic RS encoder 623 performs a systematic RS-codingprocess identical to that of the conventional receiving system on theinputted data, thereby adding the 20-byte RS parity at the end of the187-byte data. Alternatively, if the inputted data correspond to theenhanced data packet, the 20 bytes of RS parity gained by performing thenon-systematic RS-coding are respectively inserted in the decided paritybyte places within the enhanced data packet. Herein, the datainterleaver 624 corresponds to a byte unit convolutional interleaver.The output of the data interleaver 624 is inputted to the parity bytereplacer 625 and the non-systematic RS encoder 626.

Meanwhile, a memory within the trellis encoding module 627, which ispositioned after the parity byte replacer 625, should first beinitialized in order to allow the output data of the trellis encodingmodule 627 so as to become the known data defined based upon anagreement between the receiving system and the transmitting system. Morespecifically, the memory of the trellis encoding module 627 should firstbe initialized before the known data sequence being inputted istrellis-encoded. At this point, the beginning of the known data sequencethat is inputted corresponds to the initialization data place holderinserted by the group formatter 614 and not the actual known data.Therefore, a process of generating initialization data right before thetrellis-encoding of the known data sequence being inputted and a processof replacing the initialization data place holder of the correspondingtrellis encoding module memory with the newly generated initializationdata are required.

A value of the trellis memory initialization data is decided based uponthe memory status of the trellis encoding module 627, thereby generatingthe trellis memory initialization data accordingly. Due to the influenceof the replace initialization data, a process of recalculating the RSparity, thereby replacing the RS parity outputted from the trellisencoding module 627 with the newly calculated RS parity is required.Accordingly, the non-systematic RS encoder 626 receives the enhanceddata packet including the initialization data place holder that is to bereplaced with the initialization data from the data interleaver 624 andalso receives the initialization data from the trellis encoding module627. Thereafter, among the received enhanced data packet, theinitialization data place holder is replaced with the initializationdata. Subsequently, the RS parity data added to the enhanced data packetare removed. Then, a new non-systematic RS parity is calculated andoutputted to the parity byte replacer 625. Accordingly, the parity bytereplacer 625 selects the output of the data interleaver 624 as the datawithin the enhanced data packet, and selects the output of thenon-systematic RS encoder 626 as the RS parity. Thereafter, the paritybyte replacer 625 outputs the selected data.

Meanwhile, if the main data packet is inputted, or if the enhanced datapacket that does not include the initialization data place holder thatis to be replaced, the parity byte replacer 625 selects the data and RSparity outputted from the data interleaver 624 and directly outputs theselected data to the trellis encoding module 627 without modification.The trellis encoding module 627 converts the byte-unit data tosymbol-unit data and 12-way interleaves and trellis-encodes theconverted data, which are then outputted to the frame multiplexer 628.The frame multiplexer 628 inserts field synchronization and segmentsynchronization signals in the output of the trellis encoding module 627and then outputs the processed data to the transmitting unit 630.Herein, the transmitting unit 630 includes a pilot inserter 631, amodulator 632, and a radio frequency (RF) up-converter 633. Theoperation of the transmitting unit 630 is identical to the conventionaltransmitting systems. Therefore, a detailed description of the same willbe omitted for simplicity.

FIG. 9 illustrates a block diagram of a demodulating unit included inthe receiving system according to another embodiment of the presentinvention. Herein, the demodulating unit may effectively process signalstransmitted from the transmitting system shown in FIG. 6. Referring toFIG. 9, the demodulating unit includes a demodulator 701, a channelequalizer 702, a known data detector 703, a block decoder 704, anenhanced data deformatter 705, a RS frame decoder 706, an enhanced dataderandomizer 707, a data deinterleaver 708, a RS decoder 709, and a maindata derandomizer 710. For simplicity, the demodulator 701, the channelequalizer 702, the known data detector 703, the block decoder 704, theenhanced data deformatter 705, the RS frame decoder 706, and theenhanced data derandomizer 707 will be referred to as an enhanced dataprocessor. And, the data deinterleaver 708, the RS decoder 709, and themain data derandomizer 710 will be referred to as a main data processor.

More specifically, the enhanced data including known data and the maindata are received through the tuner and inputted to the demodulator 701and the known data detector 703. The demodulator 701 performs automaticgain control, carrier recovery, and timing recovery on the data that arebeing inputted, thereby creating baseband data, which are then outputtedto the equalizer 702 and the known data detector 703. The equalizer 702compensates the distortion within the channel included in thedemodulated data. Then, the equalizer 702 outputs the compensated datato the block decoder 704.

At this point, the known data detector 703 detects the known data placeinserted by the transmitting system to the input/output data of thedemodulator 701 (i.e., data prior to demodulation or data afterdemodulation). Then, along with the position information, the known datadetector 703 outputs the symbol sequence of the known data generatedfrom the corresponding position to the demodulator 701 and the equalizer702. Additionally, the known data detector 703 outputs informationenabling the block decoder 704 to identify the enhanced data beingadditionally encoded by the transmitting system and the main data thatare not additionally encoded to the block decoder 704. Furthermore,although the connection is not shown in FIG. 9, the information detectedby the known data detector 703 may be used in the overall receivingsystem and may also be used in the enhanced data formatter 705 and theRS frame decoder 706.

By using the known data symbol sequence when performing the timingrecovery or carrier recovery, the demodulating performance of thedemodulator 701 may be enhanced. Similarly, by using the known data, thechannel equalizing performance of the channel equalizer 702 may beenhanced. Furthermore, by feeding-back the decoding result of the blockdecoder 704 to the channel equalizer 702, the channel equalizingperformance may also be enhanced.

The channel equalizer 702 may perform channel equalization by using aplurality of methods. An example of estimating a channel impulseresponse (CIR) so as to perform channel equalization will be given inthe description of the present invention. Most particularly, an exampleof estimating the CIR in accordance with each region within the datagroup, which is hierarchically divided and transmitted from thetransmitting system, and applying each CIR differently will also bedescribed herein. Furthermore, by using the known data, the place andcontents of which is known in accordance with an agreement between thetransmitting system and the receiving system, and the fieldsynchronization data, so as to estimate the CIR, the present inventionmay be able to perform channel equalization with more stability.

Herein, the data group that is inputted for the equalization process isdivided into regions A to C, as shown in FIG. 7. More specifically, inthe example of the present invention, each region A, B, and C arefurther divided into regions A1 to A5, regions B1 and B2, and regions C1to C3, respectively. Referring to FIG. 7, the CIR that is estimated fromthe field synchronization data in the data structure is referred to asCIR_FS. Alternatively, the CIRs that are estimated from each of the 5known data sequences existing in region A are sequentially referred toas CIR_N0, CIR_N1, CIR_N2, CIR_N3, and CIR_N4.

As described above, the present invention uses the CIR estimated fromthe field synchronization data and the known data sequences in order toperform channel equalization on data within the data group. At thispoint, each of the estimated CIRs may be directly used in accordancewith the characteristics of each region within the data group.Alternatively, a plurality of the estimated CIRs may also be eitherinterpolated or extrapolated so as to create a new CIR, which is thenused for the channel equalization process.

Herein, when a value F(Q) of a function F(x) at a particular point Q anda value F(S) of the function F(x) at another particular point S areknown, interpolation refers to estimating a function value of a pointwithin the section between points Q and S. Linear interpolationcorresponds to the simplest form among a wide range of interpolationoperations. The linear interpolation described herein is merelyexemplary among a wide range of possible interpolation methods. And,therefore, the present invention is not limited only to the examples setforth herein.

Alternatively, when a value F(Q) of a function F(x) at a particularpoint Q and a value F(S) of the function F(x) at another particularpoint S are known, extrapolation refers to estimating a function valueof a point outside of the section between points Q and S. Linearextrapolation is the simplest form among a wide range of extrapolationoperations. Similarly, the linear extrapolation described herein ismerely exemplary among a wide range of possible extrapolation methods.And, therefore, the present invention is not limited only to theexamples set forth herein.

More specifically, in case of region C1, any one of the CIR_N4 estimatedfrom a previous data group, the CIR_FS estimated from the current datagroup that is to be processed with channel equalization, and a new CIRgenerated by extrapolating the CIR_FS of the current data group and theCIR_N0 may be used to perform channel equalization. Alternatively, incase of region B1, a variety of methods may be applied as described inthe case for region C1. For example, a new CIR created by linearlyextrapolating the CIR_FS estimated from the current data group and theCIR_N0 may be used to perform channel equalization. Also, the CIR_FSestimated from the current data group may also be used to performchannel equalization. Finally, in case of region A1, a new CIR may becreated by interpolating the CIR_FS estimated from the current datagroup and CIR_N0, which is then used to perform channel equalization.Furthermore, any one of the CIR_FS estimated from the current data groupand CIR_N0 may be used to perform channel equalization.

In case of regions A2 to A5, CIR_N(i−1) estimated from the current datagroup and CIR_N(i) may be interpolated to create a new CIR and use thenewly created CIR to perform channel equalization. Also, any one of theCIR_N(i−1) estimated from the current data group and the CIR_N(i) may beused to perform channel equalization. Alternatively, in case of regionsB2, C2, and C3, CIR_N3 and CIR_N4 both estimated from the current datagroup may be extrapolated to create a new CIR, which is then used toperform the channel equalization process. Furthermore, the CIR_N4estimated from the current data group may be used to perform the channelequalization process. Accordingly, an optimum performance may beobtained when performing channel equalization on the data inserted inthe data group. The methods of obtaining the CIRs required forperforming the channel equalization process in each region within thedata group, as described above, are merely examples given to facilitatethe understanding of the present invention. A wider range of methods mayalso be used herein. And, therefore, the present invention will not onlybe limited to the examples given in the description set forth herein.

Meanwhile, if the data being channel equalized and then inputted to theblock decoder 704 correspond to the enhanced data on which additionalencoding and trellis encoding are both performed by the transmittingsystem, trellis-decoding and additional decoding processes are performedas inverse processes of the transmitting system. Alternatively, if thedata being channel equalized and then inputted to the block decoder 704correspond to the main data on which additional encoding is notperformed and only trellis-encoding is performed by the transmittingsystem, only the trellis-decoding process is performed. The data groupdecoded by the block decoder 704 is inputted to the enhanced datadeformatter 705, and the main data packet is inputted to the datadeinterleaver 708.

More specifically, if the inputted data correspond to the main data, theblock decoder 704 performs Viterbi decoding on the inputted data, so asto either output a hard decision value or hard-decide a soft decisionvalue and output the hard-decided result. On the other hand, if theinputted correspond to the enhanced data, the block decoder 704 outputseither a hard decision value or a soft decision value on the inputtedenhanced data. In other words, if the data inputted to the block decoder704 correspond to the enhanced data, the block decoder 704 performs adecoding process on the data encoded by the block processor and thetrellis encoder of the transmitting system. At this point, the output ofthe RS frame encoder included in the pre-processor of the transmittingsystem becomes an external code, and the output of the block processorand the trellis encoder becomes an internal code. In order to showmaximum performance of the external code when decoding such connectioncodes, the decoder of the internal code should output a soft decisionvalue. Therefore, the block decoder 704 may output a hard decision valueon the enhanced data. However, when required, it is more preferable thatthe block decoder 704 outputs a soft decision value.

The present invention may also be used for configuring a reliability mapusing the soft decision value. The reliability map determines andindicates whether a byte corresponding to a group of 8 bits decided bythe code of the soft decision value is reliable. For example, when anabsolute value of the soft decision value exceeds a pre-determinedthreshold value, the value of the bit corresponding to the soft decisionvalue code is determined to be reliable. However, if the absolute valuedoes not exceed the pre-determined threshold value, then the value ofthe corresponding bit is determined to be not reliable. Further, if atleast one bit among the group of 8 bits, which are determined based uponthe soft decision value, is determined to be not reliable, then thereliability map indicates that the entire byte is not reliable. Herein,the process of determining the reliability by 1-bit units is merelyexemplary. The corresponding byte may also be indicated to be notreliable if a plurality of bits (e.g., 4 bits) is determined to be notreliable.

Conversely, when all of the bits are determined to be reliable withinone byte (i.e., when the absolute value of the soft value of all bitsexceeds the pre-determined threshold value), then the reliability mapdetermines and indicates that the corresponding data byte is reliable.Similarly, when more than 4 bits are determined to be reliable withinone data byte, then the reliability map determines and indicates thatthe corresponding data byte is reliable. The estimated numbers aremerely exemplary and do not limit the scope and spirit of the presentinvention. Herein, the reliability map may be used when performing errorcorrection decoding processes.

Meanwhile, the data deinterleaver 708, the RS decoder 709, and the maindata derandomizer 710 are blocks required for receiving the main data.These blocks may not be required in a receiving system structure thatreceives only the enhanced data. The data deinterleaver 708 performs aninverse process of the data interleaver of the transmitting system. Morespecifically, the data deinterleaver 708 deinterleaves the main databeing outputted from the block decode 704 and outputs the deinterleaveddata to the RS decoder 709. The RS decoder 709 performs systematic RSdecoding on the deinterleaved data and outputs the systematicallydecoded data to the main data derandomizer 710. The main dataderandomizer 710 receives the data outputted from the RS decoder 709 soas to generate the same pseudo random byte as that of the randomizer inthe transmitting system. The main data derandomizer 710 then performs abitwise exclusive OR (XOR) operation on the generated pseudo random databyte, thereby inserting the MPEG synchronization bytes to the beginningof each packet so as to output the data in 188-byte main data packetunits.

Herein, the format of the data being outputted to the enhanced datadeformatter 705 from the block decoder 704 is a data group format. Atthis point, the enhanced data deformatter 705 already knows thestructure of the input data. Therefore, the enhanced data deformatter705 identifies the system information including signaling informationand the enhanced data from the data group. Thereafter, the identifiedsignaling information is transmitted to where the system information isrequired, and the enhanced data are outputted to the RS frame decoder706. The enhanced data deformatter 705 removes the known data, trellisinitialization data, and MPEG header that were included in the main dataand the data group and also removes the RS parity that was added by theRS encoder/non-systematic RS encoder of the transmitting system.Thereafter, the processed data are outputted to the RS frame decoder706.

More specifically, the RS frame decoder 706 receives the RS-coded andCRC-coded enhanced data from the enhanced data deformatter 705 so as toconfigure the RS frame. The RS frame decoder 706 performs an inverseprocess of the RS frame encoder included in the transmitting system,thereby correcting the errors within the RS frame. Then, the 1-byte MPEGsynchronization byte, which was removed during the RS frame codingprocess, is added to the error corrected enhanced data packet.Subsequently, the processed data are outputted to the enhanced dataderandomizer 707. Herein, the enhanced data derandomizer 707 performs aderandomizing process, which corresponds to an inverse process of theenhanced data randomizer included in the transmitting system, on thereceived enhanced data. Then, by outputting the processed data, theenhanced data transmitted from the transmitting system can be obtained.

According to an embodiment of the present invention, the RS framedecoder 706 may also be configured as follows. The RS frame decoder 706may perform a CRC syndrome check on the RS frame, thereby verifyingwhether or not an error has occurred in each row. Subsequently, the CRCchecksum is removed and the presence of an error is indicated on a CRCerror flag corresponding to each row. Then, a RS decoding process isperformed on the RS frame having the CRC checksum removed in a columndirection. At this point, depending upon the number of CRC error flags,a RS erasure decoding process may be performed. More specifically, bychecking the CRC error flags corresponding to each row within the RSframe, the number of CRC error flags may be determined whether it isgreater or smaller than the maximum number of errors, when RS decodingthe number of rows with errors (or erroneous rows) in the columndirection. Herein, the maximum number of errors corresponds to thenumber of parity bytes inserted during the RS decoding process. As anexample of the present invention, it is assumed that 48 parity bytes areadded to each column.

If the number of rows with CRC errors is equal to or smaller than themaximum number of errors (e.g., 48 which may be corrected by the RSerasure decoding process, the RS erasure decoding process is performedon the RS frame in the column direction. Thereafter, the 48 bytes ofparity data that were added at the end of each column are removed.However, if the number of rows with CRC errors is greater than themaximum number of errors (e.g., 48), which may be corrected by the RSerasure decoding process, the RS erasure decoding process cannot beperformed. In this case, the error may be corrected by performing ageneral RS decoding process.

As another embodiment of the present invention, the error correctionability may be enhanced by using the reliability map created whenconfiguring the RS frame from the soft decision value. Morespecifically, the RS frame decoder 706 compares the absolute value ofthe soft decision value obtained from the block decoder 704 to thepre-determined threshold value so as to determine the reliability of thebit values that are decided by the code of the corresponding softdecision value. Then, 8 bits are grouped to configure a byte. Then, thereliability information of the corresponding byte is indicated on thereliability map. Therefore, even if a specific row is determined to haveCRC errors as a result of the CRC syndrome checking process of thecorresponding row, it is not assumed that all of the data bytes includedin the corresponding row have error. Instead, only the data bytes thatare determined to be not reliable, after referring to the reliabilityinformation on the reliability map, are set to have errors. In otherwords, regardless of the presence of CRC errors in the correspondingrow, only the data bytes that are determined to be not reliable (orunreliable) by the reliability map are set as erasure points.

Thereafter, if the number of erasure points for each column is equal toor smaller than the maximum number of errors (e.g., 48), the RS erasuredecoding process is performed on the corresponding the column.Conversely, if the number of erasure points is greater than the maximumnumber of errors (e.g., 48), which may be corrected by the RS erasuredecoding process, a general decoding process is performed on thecorresponding column. In other words, if the number of rows having CRCerrors is greater than the maximum number of errors (e.g., 48), whichmay be corrected by the RS erasure decoding process, either a RS erasuredecoding process or a general RS decoding process is performed on aparticular column in accordance with the number of erasure point withinthe corresponding column, wherein the number is decided based upon thereliability information on the reliability map. When the above-describedprocess is performed, the error correction decoding process is performedin the direction of all of the columns included in the RS frame.Thereafter, the 48 bytes of parity data added to the end of each columnare removed.

FIG. 10 illustrates a block diagram showing the structure of a digitalbroadcast receiving system according to an embodiment of the presentinvention. Referring to FIG. 10, the digital broadcast receiving systemincludes a tuner 801, a demodulating unit 802, a demultiplexer 803, anaudio decoder 804, a video decoder 805, a native TV application manager806, a channel manager 807, a channel map 808, a first memory 809, adata decoder 810, a second memory 811, a system manager 812, a databroadcasting application manager 813, a storage controller 814, and athird memory 815. Herein, the third memory 815 is a mass storage device,such as a hard disk drive (HDD) or a memory chip. The tuner 801 tunes afrequency of a specific channel through any one of an antenna, cable,and satellite. Then, the tuner 801 down-converts the tuned frequency toan intermediate frequency (IF), which is then outputted to thedemodulating unit 802. At this point, the tuner 801 is controlled by thechannel manager 807. Additionally, the result and strength of thebroadcast signal of the tuned channel are also reported to the channelmanager 807. The data that are being received by the frequency of thetuned specific channel include main data, enhanced data, and table datafor decoding the main data and enhanced data.

In the embodiment of the present invention, examples of the enhanceddata may include data provided for data service, such as Javaapplication data, HTML application data, XML data, and so on. The dataprovided for such data services may correspond either to a Java classfile for the Java application, or to a directory file designatingpositions (or locations) of such files. Furthermore, such data may alsocorrespond to an audio file and/or a video file used in eachapplication. The data services may include weather forecast services,traffic information services, stock information services, servicesproviding information quiz programs providing audience participationservices, real time poll, user interactive education programs, gamingservices, services providing information on soap opera (or TV series)synopsis, characters, original sound track, filing sites, servicesproviding information on past sports matches, profiles andaccomplishments of sports players, product information and productordering services, services providing information on broadcast programsby media type, airing time, subject, and so on. The types of dataservices described above are only exemplary and are not limited only tothe examples given herein. Furthermore, depending upon the embodiment ofthe present invention, the enhanced data may correspond to meta data.For example, the meta data use the XML application so as to betransmitted through a DSM-CC protocol.

The demodulating unit 802 performs demodulation and channel equalizationon the signal being outputted from the tuner 801, thereby identifyingthe main data and the enhanced data. Thereafter, the identified maindata and enhanced data are outputted in TS packet units. Examples of thedemodulating unit 802 are shown in FIG. 5 and FIG. 9. The demodulatingunit shown in FIG. 5 and FIG. 9 is merely exemplary and the scope of thepresent invention is not limited to the examples set forth herein. Inthe embodiment given as an example of the present invention, only theenhanced data packet outputted from the demodulating unit 802 isinputted to the demultiplexer 803. In this case, the main data packet isinputted to another demultiplexer (not shown) that processes main datapackets. Herein, the storage controller 814 is also connected to theother demultiplexer in order to store the main data after processing themain data packets. The demultiplexer of the present invention may alsobe designed to process both enhanced data packets and main data packetsin a single demultiplexer.

The storage controller 814 is interfaced with the demultipelxer so as tocontrol instant recording, reserved (or pre-programmed) recording, timeshift, and so on of the enhanced data and/or main data. For example,when one of instant recording, reserved (or pre-programmed) recording,and time shift is set and programmed in the receiving system (orreceiver) shown in FIG. 10, the corresponding enhanced data and/or maindata that are inputted to the demultiplexer are stored in the thirdmemory 815 in accordance with the control of the storage controller 814.The third memory 815 may be described as a temporary storage area and/ora permanent storage area. Herein, the temporary storage area is used forthe time shifting function, and the permanent storage area is used for apermanent storage of data according to the user's choice (or decision).

When the data stored in the third memory 815 need to be reproduced (orplayed), the storage controller 814 reads the corresponding data storedin the third memory 815 and outputs the read data to the correspondingdemultiplexer (e.g., the enhanced data are outputted to thedemultiplexer 803 shown in FIG. 10). At this point, according to theembodiment of the present invention, since the storage capacity of thethird memory 815 is limited, the compression encoded enhanced dataand/or main data that are being inputted are directly stored in thethird memory 815 without any modification for the efficiency of thestorage capacity. In this case, depending upon the reproduction (orreading) command, the data read from the third memory 815 pass troughthe demultiplexer so as to be inputted to the corresponding decoder,thereby being restored to the initial state.

The storage controller 814 may control the reproduction (or play),fast-forward, rewind, slow motion, instant replay functions of the datathat are already stored in the third memory 815 or presently beingbuffered. Herein, the instant replay function corresponds to repeatedlyviewing scenes that the viewer (or user) wishes to view once again. Theinstant replay function may be performed on stored data and also on datathat are currently being received in real time by associating theinstant replay function with the time shift function. If the data beinginputted correspond to the analog format, for example, if thetransmission mode is NTSC, PAL, and so on, the storage controller 814compression encodes the inputted data and stored the compression-encodeddata to the third memory 815. In order to do so, the storage controller814 may include an encoder, wherein the encoder may be embodied as oneof software, middleware, and hardware. Herein, an MPEG encoder may beused as the encoder according to an embodiment of the present invention.The encoder may also be provided outside of the storage controller 814.

Meanwhile, in order to prevent illegal duplication (or copies) of theinput data being stored in the third memory 815, the storage controller814 scrambles the input data and stores the scrambled data in the thirdmemory 815. Accordingly, the storage controller 814 may include ascramble algorithm for scrambling the data stored in the third memory815 and a descramble algorithm for descrambling the data read from thethird memory 815. Herein, the definition of scramble includesencryption, and the definition of descramble includes decryption. Thescramble method may include using an arbitrary key (e.g., control word)to modify a desired set of data, and also a method of mixing signals.

Meanwhile, the demultiplexer 803 receives the real-time data outputtedfrom the demodulating unit 802 or the data read from the third memory815 and demultiplexes the received data. In the example given in thepresent invention, the demultiplexer 803 performs demultiplexing on theenhanced data packet. Therefore, in the present invention, the receivingand processing of the enhanced data will be described in detail. Itshould also be noted that a detailed description of the processing ofthe main data will be omitted for simplicity starting from thedescription of the demultiplexer 803 and the subsequent elements.

The demultiplexer 803 demultiplexes enhanced data and program specificinformation/program and system information protocol (PSI/PSIP) tablesfrom the enhanced data packet inputted in accordance with the control ofthe data decoder 810. Thereafter, the demultiplexed enhanced data andPSI/PSIP tables are outputted to the data decoder 810 in a sectionformat. In order to extract the enhanced data from the channel throughwhich enhanced data are transmitted and to decode the extracted enhanceddata, system information is required. Such system information may alsobe referred to as service information. The system information mayinclude channel information, event information, etc. In the embodimentof the present invention, the PSI/PSIP tables are applied as the systeminformation. However, the present invention is not limited to theexample set forth herein. More specifically, regardless of the name, anyprotocol transmitting system information in a table format may beapplied in the present invention.

The PSI table is an MPEG-2 system standard defined for identifying thechannels and the programs. The PSIP table is an advanced televisionsystems committee (ATSC) standard that can identify the channels and theprograms. The PSI table may include a program association table (PAT), aconditional access table (CAT), a program map table (PMT), and a networkinformation table (NIT). Herein, the PAT corresponds to specialinformation that is transmitted by a data packet having a PID of ‘0’.The PAT transmits PID information of the PMT and PID information of theNIT corresponding to each program. The CAT transmits information on apaid broadcast system used by the transmitting system. The PMT transmitsPID information of a transport stream (TS) packet, in which programidentification numbers and individual bit sequences of video and audiodata configuring the corresponding program are transmitted, and the PIDinformation, in which PCR is transmitted. The NIT transmits informationof the actual transmission network.

The PSIP table may include a virtual channel table (VCT), a system timetable (STT), a rating region table (RRT), an extended text table (ETT),a direct channel change table (DCCT), an event information table (EIT),and a master guide table (MGT). The VCT transmits information on virtualchannels, such as channel information for selecting channels andinformation such as packet identification (PID) numbers for receivingthe audio and/or video data. More specifically, when the VCT is parsed,the PID of the audio/video data of the broadcast program may be known.Herein, the corresponding audio/video data are transmitted within thechannel along with the channel name and the channel number. The STTtransmits information on the current data and timing information. TheRRT transmits information on region and consultation organs for programratings. The ETT transmits additional description of a specific channeland broadcast program. The EIT transmits information on virtual channelevents (e.g., program title, program start time, etc.). The DCCT/DCCSCTtransmits information associated with automatic (or direct) channelchange. And, the MGT transmits the versions and PID information of theabove-mentioned tables included in the PSIP.

Each of the above-described tables included in the PSI/PSIP isconfigured of a basic unit referred to as a “section”, and a combinationof one or more sections forms a table. For example, the VCT may bedivided into 256 sections. Herein, one section may include a pluralityof virtual channel information. However, a single set of virtual channelinformation is not divided into two or more sections. At this point, thereceiving system may parse and decode the data for the data service thatare transmitting by using only the tables included in the PSI, or onlythe tables included in the PISP, or a combination of tables included inboth the PSI and the PSIP. In order to parse and decode the data for thedata service, at least one of the PAT and PMT included in the PSI, andthe VCT included in the PSIP is required. For example, the PAT mayinclude the system information for transmitting the data correspondingto the data service, and the PID of the PMT corresponding to the dataservice data (or program number). The PMT may include the PID of the TSpacket used for transmitting the data service data. The VCT may includeinformation on the virtual channel for transmitting the data servicedata, and the PID of the TS packet for transmitting the data servicedata.

Meanwhile, depending upon the embodiment of the present invention, aDVB-SI may be applied instead of the PSIP. The DVB-SI may include anetwork information table (NIT), a service description table (SDT), anevent information table (EIT), and a time and data table (TDT). TheDVB-SI may be used in combination with the above-described PSI. Herein,the NIT divides the services corresponding to particular networkproviders by specific groups. The NIT includes all tuning informationthat are used during the IRD set-up. The NIT may be used for informingor notifying any change in the tuning information. The SDT includes theservice name and different parameters associated with each servicecorresponding to a particular MPEG multiplex. The EIT is used fortransmitting information associated with all events occurring in theMPEG multiplex. The EIT includes information on the current transmissionand also includes information selectively containing differenttransmission streams that may be received by the IRD. And, the TDT isused for updating the clock included in the IRD.

Furthermore, three selective SI tables (i.e., a bouquet associate table(BAT), a running status table (RST), and a stuffing table (ST)) may alsobe included. More specifically, the bouquet associate table (BAT)provides a service grouping method enabling the IRD to provide servicesto the viewers. Each specific service may belong to at least one‘bouquet’ unit. A running status table (RST) section is used forpromptly and instantly updating at least one event execution status. Theexecution status section is transmitted only once at the changing pointof the event status. Other SI tables are generally transmitted severaltimes. The stuffing table (ST) may be used for replacing or discarding asubsidiary table or the entire SI tables.

In the present invention, the enhanced data included in the payloadwithin the TS packet consist of a digital storage media-command andcontrol (DSM-CC) section format. However, the TS packet including thedata service data may correspond either to a packetized elementarystream (PES) type or to a section type. More specifically, either thePES type data service data configure the TS packet, or the section typedata service data configure the TS packet. The TS packet configured ofthe section type data will be given as the example of the presentinvention. At this point, the data service data are includes in thedigital storage media-command and control (DSM-CC) section. Herein, theDSM-CC section is then configured of a 188-byte unit TS packet.

Furthermore, the packet identification of the TS packet configuring theDSM-CC section is included in a data service table (DST). Whentransmitting the DST, ‘0x95’ is assigned as the value of a stream_typefield included in the service location descriptor of the PMT or the VCT.More specifically, when the PMT or VCT stream_type field value is‘0x95’, the receiving system may acknowledge that data broadcastingincluding enhanced data (i.e., the enhanced data) is being received. Atthis point, the enhanced data may be transmitted by a data carouselmethod. The data carousel method corresponds to repeatedly transmittingidentical data on a regular basis.

At this point, according to the control of the data decoder 810, thedemultiplexer 803 performs section filtering, thereby discardingrepetitive sections and outputting only the non-repetitive sections tothe data decoder 810. The demultiplexer 803 may also output only thesections configuring desired tables (e.g., VCT) to the data decoder 810by section filtering. Herein, the VCT may include a specific descriptorfor the enhanced data. However, the present invention does not excludethe possibilities of the enhanced data being included in other tables,such as the PMT. The section filtering method may include a method ofverifying the PID of a table defined by the MGT, such as the VCT, priorto performing the section filtering process. Alternatively, the sectionfiltering method may also include a method of directly performing thesection filtering process without verifying the MGT, when the VCTincludes a fixed PID (i.e., a base PID). At this point, thedemultiplexer 803 performs the section filtering process by referring toa table_id field, a version_number field, a section_number field, etc.

As described above, the method of defining the PID of the VCT broadlyincludes two different methods. Herein, the PID of the VCT is a packetidentifier required for identifying the VCT from other tables. The firstmethod consists of setting the PID of the VCT so that it is dependent tothe MGT. In this case, the receiving system cannot directly verify theVCT among the many PSI and/or PSIP tables. Instead, the receiving systemmust check the PID defined in the MGT in order to read the VCT. Herein,the MGT defines the PID, size, version number, and so on, of diversetables. The second method consists of setting the PID of the VCT so thatthe PID is given a base PID value (or a fixed PID value), thereby beingindependent from the MGT. In this case, unlike in the first method, theVCT according to the present invention may be identified without havingto verify every single PID included in the MGT. Evidently, an agreementon the base PID must be previously made between the transmitting systemand the receiving system.

Meanwhile, in the embodiment of the present invention, the demultiplexer803 may output only an application information table (AIT) to the datadecoder 810 by section filtering. The AIT includes information on anapplication being operated in the receiving system for the data service.The AIT may also be referred to as an XAIT, and an AMT. Therefore, anytable including application information may correspond to the followingdescription. When the AIT is transmitted, a value of ‘0x05’ may beassigned to a stream_type field of the PMT. The AIT may includeapplication information, such as application name, application version,application priority, application ID, application status (i.e.,auto-start, user-specific settings, kill, etc.), application type (i.e.,Java or HTML), position (or location) of stream including applicationclass and data files, application platform directory, and location ofapplication icon.

In the method for detecting application information for the data serviceby using the AIT, component_tag, original_network_id,transport_stream_id, and service_id fields may be used for detecting theapplication information. The component_tag field designates anelementary stream carrying a DSI of a corresponding object carousel. Theoriginal_network_id field indicates a DVB-SI original_network_id of theTS providing transport connection. The transport_stream_id fieldindicates the MPEG TS of the TS providing transport connection, and theservice_id field indicates the DVB-SI of the service providing transportconnection. Information on a specific channel may be obtained by usingthe original_network_id field, the transport_stream_id field, and theservice_id field. The data service data, such as the application data,detected by using the above-described method may be stored in the secondmemory 811 by the data decoder 810.

The data decoder 810 parses the DSM-CC section configuring thedemultiplexed enhanced data. Then, the enhanced data corresponding tothe parsed result are stored as a database in the second memory 811. Thedata decoder 810 groups a plurality of sections having the same tableidentification (table_id) so as to configure a table, which is thenparsed. Thereafter, the parsed result is stored as a database in thesecond memory 811. At this point, by parsing data and/or sections, thedata decoder 810 reads all of the remaining actual section data that arenot section-filtered by the demultiplexer 803. Then, the data decoder810 stores the read data to the second memory 811. The second memory 811corresponds to a table and data carousel database storing systeminformation parsed from tables and enhanced data parsed from the DSM-CCsection. Herein, a table_id field, a section_number field, and alast_section_number field included in the table may be used to indicatewhether the corresponding table is configured of a single section or aplurality of sections. For example, TS packets having the PID of the VCTare grouped to form a section, and sections having table identifiersallocated to the VCT are grouped to form the VCT.

When the VCT is parsed, information on the virtual channel to whichenhanced data are transmitted may be obtained. The obtained applicationidentification information, service component identificationinformation, and service information corresponding to the data servicemay either be stored in the second memory 811 or be outputted to thedata broadcasting application manager 813. In addition, reference may bemade to the application identification information, service componentidentification information, and service information in order to decodethe data service data. Alternatively, such information may also preparethe operation of the application program for the data service.Furthermore, the data decoder 810 controls the demultiplexing of thesystem information table, which corresponds to the information tableassociated with the channel and events. Thereafter, an A.V PID list maybe transmitted to the channel manager 807.

The channel manager 807 may refer to the channel map 808 in order totransmit a request for receiving system-related information data to thedata decoder 810, thereby receiving the corresponding result. Inaddition, the channel manager 807 may also control the channel tuning ofthe tuner 801. Furthermore, the channel manager 807 may directly controlthe demultiplexer 803, so as to set up the A/V PID, thereby controllingthe audio decoder 804 and the video decoder 805. The audio decoder 804and the video decoder 805 may respectively decode and output the audiodata and video data demultiplexed from the main data packet.Alternatively, the audio decoder 804 and the video decoder 805 mayrespectively decode and output the audio data and video datademultiplexed from the enhanced data packet. Meanwhile, when theenhanced data include data service data, and also audio data and videodata, it is apparent that the audio data and video data demultiplexed bythe demultiplexer 803 are respectively decoded by the audio decoder 804and the video decoder 805. For example, an audio-coding (AC)-3 decodingalgorithm may be applied to the audio decoder 804, and a MPEG-2 decodingalgorithm may be applied to the video decoder 805.

Meanwhile, the native TV application manager 806 operates a nativeapplication program stored in the first memory 809, thereby performinggeneral functions such as channel change. The native application programrefers to software stored in the receiving system upon shipping of theproduct. More specifically, when a user request (or command) istransmitted to the receiving system through a user interface (UI), thenative TV application manger 806 displays the user request on a screenthrough a graphic user interface (GUI), thereby responding to the user'srequest. The user interface receives the user request through an inputdevice, such as a remote controller, a key pad, a jog controller, an atouch-screen provided on the screen, and then outputs the received userrequest to the native TV application manager 806 and the databroadcasting application manager 813. Furthermore, the native TVapplication manager 806 controls the channel manager 807, therebycontrolling channel-associated, such as the management of the channelmap 808, and controlling the data decoder 810. The native TV applicationmanager 806 also controls the GUI of the overall receiving system,thereby storing the user request and status of the receiving system inthe first memory 809 and restoring the stored information.

The channel manager 807 controls the tuner 801 and the data decoder 810,so as to managing the channel map 808 so that it can respond to thechannel request made by the user. More specifically, channel manager 807sends a request to the data decoder 810 so that the tables associatedwith the channels that are to be tuned are parsed. The results of theparsed tables are reported to the channel manager 807 by the datadecoder 810. Thereafter, based on the parsed results, the channelmanager 807 updates the channel map 808 and sets up a PID in thedemultiplexer 803 for demultiplexing the tables associated with the dataservice data from the enhanced data.

The system manager 812 controls the booting of the receiving system byturning the power on or off. Then, the system manager 812 stores ROMimages (including downloaded software images) in the first memory 809.More specifically, the first memory 809 stores management programs suchas operating system (OS) programs required for managing the receivingsystem and also application program executing data service functions.The application program is a program processing the data service datastored in the second memory 811 so as to provide the user with the dataservice. If the data service data are stored in the second memory 811,the corresponding data service data are processed by the above-describedapplication program or by other application programs, thereby beingprovided to the user. The management program and application programstored in the first memory 809 may be updated or corrected to a newlydownloaded program. Furthermore, the storage of the stored managementprogram and application program is maintained without being deleted evenif the power of the system is shut down. Therefore, when the power issupplied the programs may be executed without having to be newlydownloaded once again.

The application program for providing data service according to thepresent invention may either be initially stored in the first memory 809upon the shipping of the receiving system, or be stored in the first 809after being downloaded. The application program for the data service(i.e., the data service providing application program) stored in thefirst memory 809 may also be deleted, updated, and corrected.Furthermore, the data service providing application program may bedownloaded and executed along with the data service data each time thedata service data are being received.

When a data service request is transmitted through the user interface,the data broadcasting application manager 813 operates the correspondingapplication program stored in the first memory 809 so as to process therequested data, thereby providing the user with the requested dataservice. And, in order to provide such data service, the databroadcasting application manager 813 supports the graphic user interface(GUI). Herein, the data service may be provided in the form of text (orshort message service (SMS)), voice message, still image, and movingimage. The data broadcasting application manager 813 may be providedwith a platform for executing the application program stored in thefirst memory 809. The platform may be, for example, a Java virtualmachine for executing the Java program. Hereinafter, an example of thedata broadcasting application manager 813 executing the data serviceproviding application program stored in the first memory 809, so as toprocess the data service data stored in the second memory 811, therebyproviding the user with the corresponding data service will now bedescribed in detail.

Assuming that the data service corresponds to a traffic informationservice, the data service according to the present invention is providedto the user of a receiving system that is not equipped with anelectronic map and/or a GPS system in the form of at least one of a text(or short message service (SMS)), a voice message, a graphic message, astill image, and a moving image. In this case, is a GPS module ismounted on the receiving system shown in FIG. 10, the GPS modulereceives satellite signals transmitted from a plurality of low earthorbit satellites and extracts the current position (or location)information (e.g., longitude, latitude, altitude), thereby outputtingthe extracted information to the data broadcasting application manager813.

At this point, it is assumed that the electronic map includinginformation on each link and nod and other diverse graphic informationare stored in one of the second memory 811, the first memory 809, andanother memory that is not shown. More specifically, according to therequest made by the data broadcasting application manager 813, the dataservice data stored in the second memory 811 are read and inputted tothe data broadcasting application manager 813. The data broadcastingapplication manager 813 translates (or deciphers) the data service dataread from the second memory 811, thereby extracting the necessaryinformation according to the contents of the message and/or a controlsignal.

FIG. 11 illustrates a block diagram showing the structure of a digitalbroadcast (or television) receiving system according to anotherembodiment of the present invention. Referring to FIG. 11, the digitalbroadcast receiving system includes a tuner 901, a demodulating unit902, a demultiplexer 903, a first descrambler 904, an audio decoder 905,a video decoder 906, a second descrambler 907, an authentication unit908, a native TV application manager 909, a channel manager 910, achannel map 911, a first memory 912, a data decoder 913, a second memory914, a system manager 915, a data broadcasting application manager 916,a storage controller 917, a third memory 918, and a telecommunicationmodule 919. Herein, the third memory 918 is a mass storage device, suchas a hard disk drive (HDD) or a memory chip. Also, during thedescription of the digital broadcast (or television or DTV) receivingsystem shown in FIG. 11, the components that are identical to those ofthe digital broadcast receiving system of FIG. 10 will be omitted forsimplicity.

As described above, in order to provide services for preventing illegalduplication (or copies) or illegal viewing of the enhanced data and/ormain data that are transmitted by using a broadcast network, and toprovide paid broadcast services, the transmitting system may generallyscramble and transmit the broadcast contents. Therefore, the receivingsystem needs to descramble the scrambled broadcast contents in order toprovide the user with the proper broadcast contents. Furthermore, thereceiving system may generally be processed with an authenticationprocess with an authentication means before the descrambling process.Hereinafter, the receiving system including an authentication means anda descrambling means according to an embodiment of the present inventionwill now be described in detail.

According to the present invention, the receiving system may be providedwith a descrambling means receiving scrambled broadcasting contents andan authentication means authenticating (or verifying) whether thereceiving system is entitled to receive the descrambled contents.Hereinafter, the descrambling means will be referred to as first andsecond descramblers 904 and 907, and the authentication means will bereferred to as an authentication unit 908. Such naming of thecorresponding components is merely exemplary and is not limited to theterms suggested in the description of the present invention. Forexample, the units may also be referred to as a decryptor. Although FIG.11 illustrates an example of the descramblers 904 and 907 and theauthentication unit 908 being provided inside the receiving system, eachof the descramblers 904 and 907 and the authentication unit 908 may alsobe separately provided in an internal or external module. Herein, themodule may include a slot type, such as a SD or CF memory, a memorystick type, a USB type, and so on, and may be detachably fixed to thereceiving system.

As described above, when the authentication process is performedsuccessfully by the authentication unit 908, the scrambled broadcastingcontents are descrambled by the descramblers 904 and 907, thereby beingprovided to the user. At this point, a variety of the authenticationmethod and descrambling method may be used herein. However, an agreementon each corresponding method should be made between the receiving systemand the transmitting system. Hereinafter, the authentication anddescrambling methods will now be described, and the description ofidentical components or process steps will be omitted for simplicity.

The receiving system including the authentication unit 908 and thedescramblers 904 and 907 will now be described in detail. The receivingsystem receives the scrambled broadcasting contents through the tuner901 and the demodulating unit 902. Then, the system manager 915 decideswhether the received broadcasting contents have been scrambled. Herein,the demodulating unit 902 may be included as a demodulating meansaccording to embodiments of the present invention as described in FIG. 5and FIG. 9. However, the present invention is not limited to theexamples given in the description set forth herein. If the systemmanager 915 decides that the received broadcasting contents have beenscrambled, then the system manager 915 controls the system to operatethe authentication unit 908. As described above, the authentication unit908 performs an authentication process in order to decide whether thereceiving system according to the present invention corresponds to alegitimate host entitled to receive the paid broadcasting service.Herein, the authentication process may vary in accordance with theauthentication methods.

For example, the authentication unit 908 may perform the authenticationprocess by comparing an IP address of an IP datagram within the receivedbroadcasting contents with a specific address of a corresponding host.At this point, the specific address of the corresponding receivingsystem (or host) may be a MAC address. More specifically, theauthentication unit 908 may extract the IP address from the decapsulatedIP datagram, thereby obtaining the receiving system information that ismapped with the IP address. At this point, the receiving system shouldbe provided, in advance, with information (e.g., a table format) thatcan map the IP address and the receiving system information.Accordingly, the authentication unit 908 performs the authenticationprocess by determining the conformity between the address of thecorresponding receiving system and the system information of thereceiving system that is mapped with the IP address. In other words, ifthe authentication unit 908 determines that the two types of informationconform to one another, then the authentication unit 908 determines thatthe receiving system is entitled to receive the correspondingbroadcasting contents.

In another example, standardized identification information is definedin advance by the receiving system and the transmitting system. Then,the identification information of the receiving system requesting thepaid broadcasting service is transmitted by the transmitting system.Thereafter, the receiving system determines whether the receivedidentification information conforms with its own unique identificationnumber, so as to perform the authentication process. More specifically,the transmitting system creates a database for storing theidentification information (or number) of the receiving systemrequesting the paid broadcasting service. Then, if the correspondingbroadcasting contents are scrambled, the transmitting system includesthe identification information in the EMM, which is then transmitted tothe receiving system.

If the corresponding broadcasting contents are scrambled, messages(e.g., entitlement control message (ECM), entitlement management message(EMM)), such as the CAS information, mode information, message positioninformation, that are applied to the scrambling of the broadcastingcontents are transmitted through a corresponding data header or antherdata packet. The ECM may include a control word (CW) used for scramblingthe broadcasting contents. At this point, the control word may beencoded with an authentication key. The EMM may include anauthentication key and entitlement information of the correspondingdata. Herein, the authentication key may be encoded with a receivingsystem-specific distribution key. In other words, assuming that theenhanced data are scrambled by using the control word, and that theauthentication information and the descrambling information aretransmitted from the transmitting system, the transmitting systemencodes the CW with the authentication key and, then, includes theencoded CW in the entitlement control message (ECM), which is thentransmitted to the receiving system. Furthermore, the transmittingsystem includes the authentication key used for encoding the CW and theentitlement to receive data (or services) of the receiving system (i.e.,a standardized serial number of the receiving system that is entitled toreceive the corresponding broadcasting service or data) in theentitlement management message (EMM), which is then transmitted to thereceiving system.

Accordingly, the authentication unit 908 of the receiving systemextracts the identification information of the receiving system and theidentification information included in the EMM of the broadcastingservice that is being received. Then, the authentication unit 908determines whether the identification information conform to each other,so as to perform the authentication process. More specifically, if theauthentication unit 90B determines that the information conform to eachother, then the authentication unit 908 eventually determines that thereceiving system is entitled to receive the request broadcastingservice.

In yet another example, the authentication unit 908 of the receivingsystem may be detachably fixed to an external module. In this case, thereceiving system is interfaced with the external module through a commoninterface (CI). In other words, the external module may receive the datascrambled by the receiving system through the common interface, therebyperforming the descrambling process of the received data. Alternatively,the external module may also transmit only the information required forthe descrambling process to the receiving system. The common interfaceis configured on a physical layer and at least one protocol layer.Herein, in consideration of any possible expansion of the protocol layerin a later process, the corresponding protocol layer may be configuredto have at least one layer that can each provide an independentfunction.

The external module may either consist of a memory or card havinginformation on the key used for the scrambling process and otherauthentication information but not including any descrambling function,or consist of a card having the above-mentioned key information andauthentication information and including the descrambling function. Boththe receiving system and the external module should be authenticated inorder to provide the user with the paid broadcasting service provided(or transmitted) from the transmitting system. Therefore, thetransmitting system can only provide the corresponding paid broadcastingservice to the authenticated pair of receiving system and externalmodule.

Additionally, an authentication process should also be performed betweenthe receiving system and the external module through the commoninterface. More specifically, the module may communicate with the systemmanager 915 included in the receiving system through the commoninterface, thereby authenticating the receiving system. Alternatively,the receiving system may authenticate the module through the commoninterface. Furthermore, during the authentication process, the modulemay extract the unique ID of the receiving system and its own unique IDand transmit the extracted IDs to the transmitting system. Thus, thetransmitting system may use the transmitted ID values as informationdetermining whether to start the requested service or as paymentinformation. Whenever necessary, the system manager 915 transmits thepayment information to the remote transmitting system through thetelecommunication module 919.

The authentication unit 908 authenticates the corresponding receivingsystem and/or the external module. Then, if the authentication processis successfully completed, the authentication unit 908 certifies thecorresponding receiving system and/or the external module as alegitimate system and/or module entitled to receive the requested paidbroadcasting service. In addition, the authentication unit 908 may alsoreceive authentication-associated information from a mobiletelecommunications service provider to which the user of the receivingsystem is subscribed, instead of the transmitting system providing therequested broadcasting service. In this case, theauthentication-association information may either be scrambled by thetransmitting system providing the broadcasting service and, then,transmitted to the user through the mobile telecommunications serviceprovider, or be directly scrambled and transmitted by the mobiletelecommunications service provider. Once the authentication process issuccessfully completed by the authentication unit 908, the receivingsystem may descramble the scrambled broadcasting contents received fromthe transmitting system. At this point, the descrambling process isperformed by the first and second descramblers 904 and 907. Herein, thefirst and second descramblers 904 and 907 may be included in an internalmodule or an external module of the receiving system.

The receiving system is also provided with a common interface forcommunicating with the external module including the first and seconddescramblers 904 and 907, so as to perform the descrambling process.More specifically, the first and second descramblers 904 and 907 may beincluded in the module or in the receiving system in the form ofhardware, middleware or software. Herein, the descramblers 904 and 907may be included in any one of or both of the module and the receivingsystem. If the first and second descramblers 904 and 907 are providedinside the receiving system, it is advantageous to have the transmittingsystem (i.e., at least any one of a service provider and a broadcaststation) scramble the corresponding data using the same scramblingmethod.

Alternatively, if the first and second descramblers 904 and 907 areprovided in the external module, it is advantageous to have eachtransmitting system scramble the corresponding data using differentscrambling methods. In this case, the receiving system is not requiredto be provided with the descrambling algorithm corresponding to eachtransmitting system. Therefore, the structure and size of receivingsystem may be simplified and more compact. Accordingly, in this case,the external module itself may be able to provide CA functions, whichare uniquely and only provided by each transmitting systems, andfunctions related to each service that is to be provided to the user.The common interface enables the various external modules and the systemmanager 915, which is included in the receiving system, to communicatewith one another by a single communication method. Furthermore, sincethe receiving system may be operated by being connected with at leastone or more modules providing different services, the receiving systemmay be connected to a plurality of modules and controllers.

In order to maintain successful communication between the receivingsystem and the external module, the common interface protocol includes afunction of periodically checking the status of the oppositecorrespondent. By using this function, the receiving system and theexternal module is capable of managing the status of each oppositecorrespondent. This function also reports the user or the transmittingsystem of any malfunction that may occur in any one of the receivingsystem and the external module and attempts the recovery of themalfunction.

In yet another example, the authentication process may be performedthrough software. More specifically, when a memory card having CASsoftware downloaded, for example, and stored therein in advanced isinserted in the receiving system, the receiving system receives andloads the CAS software from the memory card so as to perform theauthentication process. In this example, the CAS software is read outfrom the memory card and stored in the first memory 912 of the receivingsystem. Thereafter, the CAS software is operated in the receiving systemas an application program. According to an embodiment of the presentinvention, the CAS software is mounted on (or stored) in a middlewareplatform and, then executed. A Java middleware will be given as anexample of the middleware included in the present invention. Herein, theCAS software should at least include information required for theauthentication process and also information required for thedescrambling process.

Therefore, the authentication unit 908 performs authentication processesbetween the transmitting system and the receiving system and alsobetween the receiving system and the memory card. At this point, asdescribed above, the memory card should be entitled to receive thecorresponding data and should include information on a normal receivingsystem that can be authenticated. For example, information on thereceiving system may include a unique number, such as a standardizedserial number of the corresponding receiving system. Accordingly, theauthentication unit 908 compares the standardized serial number includedin the memory card with the unique information of the receiving system,thereby performing the authentication process between the receivingsystem and the memory card.

If the CAS software is first executed in the Java middleware base, thenthe authentication between the receiving system and the memory card isperformed. For example, when the unique number of the receiving systemstored in the memory card conforms to the unique number of the receivingsystem read from the system manager 915, then the memory card isverified and determined to be a normal memory card that may be used inthe receiving system. At this point, the CAS software may either beinstalled in the first memory 912 upon the shipping of the presentinvention, or be downloaded to the first memory 912 from thetransmitting system or the module or memory card, as described above.Herein, the descrambling function may be operated by the databroadcasting application manger 916 as an application program.

Thereafter, the CAS software parses the EMM/ECM packets outputted fromthe demultiplexer 903, so as to verify whether the receiving system isentitled to receive the corresponding data, thereby obtaining theinformation required for descrambling (i.e., the CW) and providing theobtained CW to the descramblers 904 and 907. More specifically, the CASsoftware operating in the Java middleware platform first reads out theunique (or serial) number of the receiving system from the correspondingreceiving system and compares it with the unique number of the receivingsystem transmitted through the EMM, thereby verifying whether thereceiving system is entitled to receive the corresponding data. Once thereceiving entitlement of the receiving system is verified, thecorresponding broadcasting service information transmitted to the ECMand the entitlement of receiving the corresponding broadcasting serviceare used to verify whether the receiving system is entitled to receivethe corresponding broadcasting service. Once the receiving system isverified to be entitled to receive the corresponding broadcastingservice, the authentication key transmitted to the EMM is used to decode(or decipher) the encoded CW, which is transmitted to the ECM, therebytransmitting the decoded CW to the descramblers 904 and 907. Each of thedescramblers 904 and 907 uses the CW to descramble the broadcastingservice.

Meanwhile, the CAS software stored in the memory card may be expanded inaccordance with the paid service which the broadcast station is toprovide. Additionally, the CAS software may also include otheradditional information other than the information associated with theauthentication and descrambling. Furthermore, the receiving system maydownload the CAS software from the transmitting system so as to upgrade(or update) the CAS software originally stored in the memory card. Asdescribed above, regardless of the type of broadcast receiving system,as long as an external memory interface is provided, the presentinvention may embody a CAS system that can meet the requirements of alltypes of memory card that may be detachably fixed to the receivingsystem. Thus, the present invention may realize maximum performance ofthe receiving system with minimum fabrication cost, wherein thereceiving system may receive paid broadcasting contents such asbroadcast programs, thereby acknowledging and regarding the variety ofthe receiving system. Moreover, since only the minimum applicationprogram interface is required to be embodied in the embodiment of thepresent invention, the fabrication cost may be minimized, therebyeliminating the manufacturer's dependence on CAS manufacturers.Accordingly, fabrication costs of CAS equipments and management systemsmay also be minimized.

Meanwhile, the descramblers 904 and 907 may be included in the moduleeither in the form of hardware or in the form of software. In this case,the scrambled data that being received are descrambled by the module andthen demodulated. Also, if the scrambled data that are being receivedare stored in the third memory 918, the received data may be descrambledand then stored, or stored in the memory at the point of being receivedand then descrambled later on prior to being played (or reproduced).Thereafter, in case scramble/descramble algorithms are provided in thestorage controller 917, the storage controller 917 scrambles the datathat are being received once again and then stores the re-scrambled datato the third memory 918.

In yet another example, the descrambled broadcasting contents(transmission of which being restricted) are transmitted through thebroadcasting network. Also, information associated with theauthentication and descrambling of data in order to disable thereceiving restrictions of the corresponding data are transmitted and/orreceived through the telecommunications module 919. Thus, the receivingsystem is able to perform reciprocal (or two-way) communication. Thereceiving system may either transmit data to the telecommunicationmodule within the transmitting system or be provided with the data fromthe telecommunication module within the transmitting system. Herein, thedata correspond to broadcasting data that are desired to be transmittedto or from the transmitting system, and also unique information (i.e.,identification information) such as a serial number of the receivingsystem or MAC address.

The telecommunication module 919 included in the receiving systemprovides a protocol required for performing reciprocal (or two-way)communication between the receiving system, which does not support thereciprocal communication function, and the telecommunication moduleincluded in the transmitting system. Furthermore, the receiving systemconfigures a protocol data unit (PDU) using a tag-length-value (TLV)coding method including the data that are to be transmitted and theunique information (or ID information). Herein, the tag field includesindexing of the corresponding PDU. The length field includes the lengthof the value field. And, the value field includes the actual data thatare to be transmitted and the unique number (e.g., identificationnumber) of the receiving system.

The receiving system may configure a platform that is equipped with theJava platform and that is operated after downloading the Javaapplication of the transmitting system to the receiving system throughthe network. In this case, a structure of downloading the PDU includingthe tag field arbitrarily defined by the transmitting system from astorage means included in the receiving system and then transmitting thedownloaded PDU to the telecommunication module 919 may also beconfigured. Also, the PDU may be configured in the Java application ofthe receiving system and then outputted to the telecommunication module919. The PDU may also be configured by transmitting the tag value, theactual data that are to be transmitted, the unique information of thecorresponding receiving system from the Java application and byperforming the TLV coding process in the receiving system. Thisstructure is advantageous in that the firmware of the receiving systemis not required to be changed even if the data (or application) desiredby the transmitting system is added.

The telecommunication module within the transmitting system eithertransmits the PDU received from the receiving system through a wirelessdata network or configures the data received through the network into aPDU which is transmitted to the host. At this point, when configuringthe PDU that is to be transmitted to the host, the telecommunicationmodule within the transmitting end may include unique information (e.g.,IP address) of the transmitting system which is located in a remotelocation. Additionally, in receiving and transmitting data through thewireless data network, the receiving system may be provided with acommon interface, and also provided with a WAP, CDMA 1×EV-DQ, which canbe connected through a mobile telecommunication base station, such asCDMA and GSM, and also provided with a wireless LAN, mobile Internet,WiBro, WiMax, which can be connected through an access point. Theabove-described receiving system corresponds to the system that is notequipped with a telecommunication function. However, a receiving systemequipped with telecommunication function does not require thetelecommunication module 919.

The broadcasting data being transmitted and received through theabove-described wireless data network may include data required forperforming the function of limiting data reception. Meanwhile, thedemultiplexer 903 receives either the real-time data outputted from thedemodulating unit 902 or the data read from the third memory 918,thereby performing demultiplexing. In this embodiment of the presentinvention, the demultiplexer 903 performs demultiplexing on the enhanceddata packet. Similar process steps have already been described earlierin the description of the present invention. Therefore, a detailed ofthe process of demultiplexing the enhanced data will be omitted forsimplicity.

The first descrambler 904 receives the demultiplexed signals from thedemultiplexer 903 and then descrambles the received signals. At thispoint, the first descrambler 904 may receive the authentication resultreceived from the authentication unit 908 and other data required forthe descrambling process, so as to perform the descrambling process. Theaudio decoder 905 and the video decoder 906 receive the signalsdescrambled by the first descrambler 904, which are then decoded andoutputted. Alternatively, if the first descrambler 904 did not performthe descrambling process, then the audio decoder 905 and the videodecoder 906 directly decode and output the received signals. In thiscase, the decoded signals are received and then descrambled by thesecond descrambler 907 and processed accordingly.

As described above, the present invention has the following advantages.More specifically, the present invention is highly protected against (orresistant to) any error that may occur when transmitting supplementaldata through a channel. And, the present invention is also highlycompatible to the conventional receiving system. Moreover, the presentinvention may also receive the supplemental data without any error evenin channels having severe ghost effect and noise.

Furthermore, by estimating and removing (or canceling) an amount ofphase change of a channel impulse response (CIR) estimated from theinputted data, the phase change is prevented from being compensated bythe channel equalizer. Thus, the present invention maximizes theperformance of a remaining carrier phase compensation loop, therebyenhancing the receiving performance of the receiving system in asituation undergoing severe and frequent channel changes. Finally, thepresent invention is even more effective when applied to mobile andportable receivers, which are also liable to a frequent change inchannel and which require protection (or resistance) against intensenoise.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1-25. (canceled)
 26. A transmitting system comprising: a first encoder for performing Reed-Solomon (RS) encoding and Cyclic Redundancy Check (CRC) encoding on enhanced data to generate an RS frame, wherein the RS frame comprises an RS frame payload including the enhanced data, RS parity data added at bottom ends of columns of the RS frame payload and Cyclic Redundancy Check (CRC) data added at right ends of rows of the RS frame payload having the RS parity data; a second encoder for encoding data in the RS frame at a code rate of 1/H, wherein H>1; a first interleaver for interleaving the encoded data in symbol units according to the following equation: P(i)={S×i×(i+1)/2} mod L, wherein 0≦i≦L−1, L=2^(n), wherein n and S are integers; a first multiplexer for multiplexing enhanced data packets including the interleaved data with main data packets including main data; and a second interleaver for interleaving data in the multiplexed data packets, thereby outputting data groups, wherein each of the data groups comprises a first region having a plurality of segments, a second region having a plurality of segments and a third region having a plurality of segments, the second region being positioned between the first and third regions, the first and third regions including main data, RS parity data and enhanced data, the second region including enhanced data, known data sequences, signaling information and RS parity data but no main data, wherein at least two segments in the second region have different start positions of the known data sequences and wherein at least two of the known data sequences are spaced 16 segments apart.
 27. The transmitting system of claim 26, further comprising: a third encoder for RS encoding the enhanced data packets of the multiplexed data packets with a non-systematic RS encoding scheme and RS encoding the main data packets of the multiplexed data packets with a systematic RS encoding scheme.
 28. The transmitting system of claim 26, further comprising: a fourth encoder for trellis encoding the interleaved data, wherein at least one memory included in the trellis encoder is initialized at each start of the known data sequences.
 29. The transmitting system of claim 28, further comprising: a second multiplexer for multiplexing the trellis-encoded data with segment synchronization data and field synchronization data.
 30. A method of processing broadcast data in a transmitting system, the method comprising: performing, by a first encoder, Reed-Solomon (RS) encoding and Cyclic Redundancy Check (CRC) encoding on enhanced data to generate an RS frame, wherein the RS frame comprises an RS frame payload including the enhanced data, RS parity data added at bottom ends of columns of the RS frame payload and Cyclic Redundancy Check (CRC) data added at right ends of rows of the RS frame payload having the RS parity data; encoding, by a second encoder, data in the RS frame at a code rate of 1/H, wherein H>1; interleaving, by a first interleaver, the encoded data in symbol units according to the following equation: P(i)={S×i×(i+1)/2} mod L, wherein 0≦i≦L−1, L=2^(n), wherein n and S are integers; multiplexing enhanced data packets including the interleaved data with main data packets including main data; and interleaving, by a second interleaver, data in the multiplexed data packets, thereby outputting data groups, wherein each of the data groups comprises a first region having a plurality of segments, a second region having a plurality of segments and a third region having a plurality of segments, the second region being positioned between the first and third regions, the first and third regions including main data, RS parity data and enhanced data, the second region including enhanced data, known data sequences, signaling information and RS parity data but no main data, wherein at least two segments in the second region have different start positions of the known data sequences and wherein at least two of the known data sequences are spaced 16 segments apart.
 31. The method of claim 30, further comprising: RS encoding the enhanced data packets of the multiplexed data packets with a non-systematic RS encoding scheme and RS encoding the main data packets of the multiplexed data packets with a systematic RS encoding scheme.
 32. The method of claim 30, further comprising: trellis encoding the interleaved data, wherein at least one memory included in the trellis encoder is initialized at each start of the known data sequences.
 33. The method of claim 32, further comprising: multiplexing the trellis-encoded data with segment synchronization data and field synchronization data. 